Biological Conversion of Biomass Residues and Waste Streams for the Sustainable Production of Biofuels and Bio-Based Products

A special issue of Fermentation (ISSN 2311-5637). This special issue belongs to the section "Fermentation Process Design".

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 43499

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Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK
Interests: biopolymers; biosurfactants/emulsifiers; waste and biomass valorization; microbial biotechnology; biorefineries
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Special Issue Information

Dear Colleagues,

One of the priorities of our modern society today is to set out a credible pathway toward the development of the circular economy and bioeconomy sectors. For such a venture to reach its full potential, sustainable and circular management of renewable resources is required, supported by innovative technologies for the prevention and removal of pollutants. Lowering the use of non-renewable raw materials results in reducing greenhouse gas emissions and environmental footprint, promotes carbon neutrality and resource efficiency, and helps to develop innovative and sustainable value chains in the biobased sector. The transformation of biological resources via biotechnological routes is crucial for developing greener industrial processes and products with perceived benefits to the health of the consumer and our ecosystems.

The aim of this Special Issue is to present current research advances and challenges in bioprocess engineering, regarding the valorization of biomass residues and waste streams, and its potential toward the production of a wide range of biofuels and biobased products, such as food, feed, biopolymers, biosurfactants, organic acids, and various fine chemicals. Such studies may include but are not limited to metabolic engineering, bioprocess engineering strategies, optimization studies, multiproduct biorefinery platforms, production capacity of underexploited microorganisms, as well as the production and characterization of novel biobased products.

Dr. Konstantina Kourmentza
Guest Editor

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Keywords

  • metabolic engineering
  • gas fermentation
  • industrial biotechnology
  • bioprocess engineering
  • renewable raw materials
  • microbial fermentation
  • photosynthetic microorganisms
  • natural products

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Published Papers (18 papers)

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12 pages, 1721 KiB  
Article
Integrated Sustainability Score Implementation as an Objective Function in Sustainable Metabolic Engineering
by Reinis Muiznieks, Elina Dace and Egils Stalidzans
Fermentation 2023, 9(6), 548; https://doi.org/10.3390/fermentation9060548 - 07 Jun 2023
Cited by 2 | Viewed by 901
Abstract
The sustainable metabolic engineering (SME) concept was defined by Stalidzans and Dace as an approach to the selection of the most sustainable metabolic engineering designs taking the economic, environmental and social components of sustainability into account. At the centre of the sustainability calculations [...] Read more.
The sustainable metabolic engineering (SME) concept was defined by Stalidzans and Dace as an approach to the selection of the most sustainable metabolic engineering designs taking the economic, environmental and social components of sustainability into account. At the centre of the sustainability calculations is a genome-scale metabolic model that provides full balance of all incoming and outgoing metabolic fluxes at steady state. Therefore, sustainability indicators are assigned for each exchange reaction, enabling the calculation of sustainability features of consumption or production of each metabolite. The further development of the SME concept depends on its implementation at the computational level to acquire applicable results—sustainable production strain designs. This study proposes for the first time a workflow and tools of SME implementation using constraint-based stoichiometric modelling, genome-scale metabolic models and growth-coupled product synthesis approach. To demonstrate the application of SME, a relatively simple engineering task has been carried out. The most sustainable designs have been identified using Escherichia coli as the chassis organism, glucose as a substrate and gene deletions as a metabolic engineering tool. A growth-coupled production design tool has been used to reduce the variability of sustainability. The 10,000 most sustainable designs are found to produce succinate as the main product with the number of deleted genes ranging from two to seven. Many similar designs were identified due to the combinatorial explosion of different alternative combinations of gene deletion sets that have the same impact on the metabolism. Full article
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17 pages, 2603 KiB  
Article
Impact of Waste as a Substrate on Biomass Formation, and Optimization of Spent Microbial Biomass Re-Use by Sustainable Metabolic Engineering
by Anna Stikane, Matiss Ricards Baumanis, Reinis Muiznieks and Egils Stalidzans
Fermentation 2023, 9(6), 531; https://doi.org/10.3390/fermentation9060531 - 30 May 2023
Cited by 2 | Viewed by 1772
Abstract
Biomass residue and waste stream bioconversion is a key pillar for successful transition toward sustainable bioeconomy. Spent microbial biomass (SMB) is a unique type of nutrient-rich residue generated from fermentation. This study addresses the waste–SMB–substrate cycle in fermentation. Data from a range of [...] Read more.
Biomass residue and waste stream bioconversion is a key pillar for successful transition toward sustainable bioeconomy. Spent microbial biomass (SMB) is a unique type of nutrient-rich residue generated from fermentation. This study addresses the waste–SMB–substrate cycle in fermentation. Data from a range of published fermentation processes using waste and non-waste substrates are analyzed for a variety of fermentation products including alcohols and biofuels, amino acids, polymers (PHA), and organic acids. On average, fermentation of waste substrates produces similar, or up to two–three times higher, amounts of SMB compared to purified substrates. SMB production from waste substrates is further illustrated with data from PHA production. The amino acid composition of SMB from 6 industrially relevant microorganisms is compared and shows relatively low variety (2–8%). The return of SMB as a (co-)substrate in fermentation is then considered by building upon the novel concept of sustainable metabolic engineering (SME). SME incorporates economic, environmental, and social sustainability criteria in its optimization algorithm to select microbial strain designs resulting in the most sustainable products. An example of SME application for SMB amino acid re-use by engineered Escherichia coli is demonstrated and discussed. A design with dual production of succinate and ethanol was found to be the most sustainable. Full article
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15 pages, 2510 KiB  
Article
Microbiome Characterization after Aerobic Digestate Reactivation of Anaerobically Digested Sewage Sludge
by Pascal Otto, Mozhdeh Alipoursarbani, Daniel Torrent, Adriel Latorre-Pérez, Thomas Paust, Alfred Albert and Christian Abendroth
Fermentation 2023, 9(5), 471; https://doi.org/10.3390/fermentation9050471 - 13 May 2023
Viewed by 2130
Abstract
A demonstrator plant of a recently patented process for improved sludge degradation has been implemented on a municipal scale. In a 1500 m3 sewage sludge digester, an intermediary stage with aerobic sewage sludge reactivation was implemented. This oxic activation increased the biogas [...] Read more.
A demonstrator plant of a recently patented process for improved sludge degradation has been implemented on a municipal scale. In a 1500 m3 sewage sludge digester, an intermediary stage with aerobic sewage sludge reactivation was implemented. This oxic activation increased the biogas yield by up to 55% with a 25% reduction of the remaining fermentation residue volume. Furthermore, this process allowed an NH4-N removal of over 90%. Additionally, 16S rRNA gene amplicon high-throughput sequencing of the reactivated digestate showed a reduced number of methane-forming archaea compared to the main digester. Multiple ammonium-oxidizing bacteria were detected. This includes multiple genera belonging to the family Chitinophagaceae (the highest values reached 18.8% of the DNA sequences) as well as a small amount of the genus Candidatus nitrosoglobus (<0.3%). In summary, the process described here provides an economically viable method to eliminate nitrogen from sewage sludge while achieving higher biogas yields and fewer potential pathogens in the residuals. Full article
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18 pages, 7386 KiB  
Article
Effect of Pretreatments on the Production of Biogas from Castor Waste by Anaerobic Digestion
by Diana Laura Quezada-Morales, Juan Campos-Guillén, Francisco Javier De Moure-Flores, Aldo Amaro-Reyes, Juan Humberto Martínez-Martínez, Ricardo Chaparro-Sánchez, Carlos Eduardo Zavala-Gómez, Antonio Flores-Macías, Rodolfo Figueroa-Brito, José Alberto Rodríguez-Morales and Miguel Angel Ramos-López
Fermentation 2023, 9(4), 399; https://doi.org/10.3390/fermentation9040399 - 20 Apr 2023
Cited by 4 | Viewed by 1366
Abstract
Lignocellulosic biomass is a source of carbohydrates that can be used in the production of biogas. The aim of this study was to obtain biogas from biomass waste (leaves, stems and seed bagasse) of Ricinus communis, applying pretreatments such as temperature and [...] Read more.
Lignocellulosic biomass is a source of carbohydrates that can be used in the production of biogas. The aim of this study was to obtain biogas from biomass waste (leaves, stems and seed bagasse) of Ricinus communis, applying pretreatments such as temperature and humidity. We examined the effect of these pretreatments on the biomass, two enzymatic pretreatments (cellulase and cellobiohydrolase), two chemicals (NaOH and HCl) and two controls (dried castor straw and seed bagasse) on the methane content. The experiment was performed in two anaerobic digestion (AD) assays at a controlled temperature (37 °C) and at room temperature, with a hydraulic retention time (HRT) of 55 days. The results showed that the residues of the seed bagasse produced the highest biogas yields both at room temperature and at the controlled temperature since this material at 37 °C produced 460.63 mL gVS−1 under cellulase pretreatment; at room temperature, the highest level of production was found for the control (263.41 mL gVS−1). The lowest yields at the controlled temperature and room temperature were obtained from residues of Ricinus communis treated with cellobiohydrolase and the seed bagasse treated with alkaline (15.15 mL gVS−1 and 78.51 mL gVS−1, respectively). Meanwhile, the greatest amount of methane was produced by seed bagasse treated with cellobiohydrolase at a controlled temperature (92.2% CH4) and the lowest content of CH4 (15.5%) was obtained at a controlled temperature from castor straw under the control treatment. Full article
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10 pages, 733 KiB  
Article
Investigation of a Broad-Bean Based Low-Cost Medium Formulation for Bacillus subtilis MSCL 897 Spore Production
by Oskars Grigs, Elina Didrihsone and Emils Bolmanis
Fermentation 2023, 9(4), 390; https://doi.org/10.3390/fermentation9040390 - 17 Apr 2023
Cited by 1 | Viewed by 1105
Abstract
Bacillus subtilis (Bs) is a bacterium that benefits plants and is used in the production of bio-fungicides. The cultivation of Bs is a crucial step in bio-control preparation production, as it greatly impacts the quality and price of the final product. In a [...] Read more.
Bacillus subtilis (Bs) is a bacterium that benefits plants and is used in the production of bio-fungicides. The cultivation of Bs is a crucial step in bio-control preparation production, as it greatly impacts the quality and price of the final product. In a series of shake flask experiments, we investigated the economically feasible broth composition for spore production of Bacillus subtilis MSCL 897, a Latvian soil isolate. Our study investigated the impact of utilizing legume-based flours (such as broad bean, grey pea, and soybean) as the primary nitrogen source, along with sugar-beet molasses, sucrose, or glucose as the carbon source, and yeast extract, peptone, and corn-steep liquor as growth factor additives. Additionally, we examined the effect of using (NH4)2HPO4 or urea as supplementary nitrogen sources, as well as previously established media formulations, on spore yield. Our results showed that a culture medium composed of broad bean flour (10 g/L) and molasses (10 g/L) led to spore productivity of 1.35 ± 0.47 × 108 CFU/mL at 48 h. By enriching the culture medium base constituents with a minor (0.5–1.0 g/L) yeast extract or corn-steep liquor additive, a notable increase in spore productivity was observed, with values of 2.00 ± 0.28 × 108 and 2.34 ± 0.18 × 108 CFU/mL at 48 h, respectively, and sporulation efficiency > 80–90%. As a result, we achieved a high spore yield of the Bacillus subtilis MSCL 897 strain, demonstrating the competitiveness of our approach, which relied on a low-cost medium made mainly from locally available and renewable raw materials. Full article
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21 pages, 1640 KiB  
Article
Enhancement of Biomass and Protein Production of Chlorella protothecoides in Heterotrophic Cultivation Using Expired Juices as Alternative Source of Nutrients for an Added-Value Biorefinery Scheme
by Jone Ibarruri, Mikel Manso and Marta Cebrián
Fermentation 2023, 9(4), 360; https://doi.org/10.3390/fermentation9040360 - 06 Apr 2023
Viewed by 2154
Abstract
Microalgae are among the most suitable sources of new protein ingredients and bioactive compounds, although their cost-effective production still remains a developmental bottleneck. Heterotrophic growth has advantages, such as higher productivity and non-dependence on light and CO2, but it has not [...] Read more.
Microalgae are among the most suitable sources of new protein ingredients and bioactive compounds, although their cost-effective production still remains a developmental bottleneck. Heterotrophic growth has advantages, such as higher productivity and non-dependence on light and CO2, but it has not yet been fully implemented. The aim of this study was to increase the biomass and protein of Chlorella protothecoides in heterotrophic conditions using expired fruit and vegetable juices (FVJ) and to compare the results to those obtained using a modified Bristol (MB) medium. The initial amounts of sugars (15 g L−1) and yeast extract (8 g L−1) led to the highest protein production (43%) and protein yield (5.2 g L−1) in trials using 1 L bottles. Bioreactor trials using FVJ resulted in a similar biomass productivity (2.94 g L−1 d−1) compared to MB (3.04 g L−1 d−1) and in enhanced polyunsaturated fatty acid content; nonetheless, a lower amount of essential amino acids (EAA) was obtained. Biomass was further processed by ultra-high-pressure homogenisation for protein concentration and residual pellet production. The protein extracts showed significant increases in EAA (11.8% and 26% increase in MB and FVJ, respectively). Residual biomass showed potential as a source of lutein and antimicrobial compounds. The results indicate that FVJ is a promising source of nutrients for the heterotrophic production of C. protothecoides, and that the extracts obtained present nutritional profiles and bioactivities of potential interest. Full article
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18 pages, 3390 KiB  
Article
Feasible Utilization of Waste Limestone as a Calcium Source for Microbially Induced Carbonate Precipitation (MICP)
by Qian Feng, Yuqi Song, Chuanwei Lu, Hao Fang, Yuxin Huang, Liuxia Chen and Xiangyang Song
Fermentation 2023, 9(3), 307; https://doi.org/10.3390/fermentation9030307 - 21 Mar 2023
Cited by 5 | Viewed by 2154
Abstract
Microbial-induced CaCO3 precipitation (MICP) is an innovative and rapidly developing technology for sand solidification. The idea for this research project was built based on the concept of sustainable development and environmental protection. The specific material used for solidification was soluble calcium ions [...] Read more.
Microbial-induced CaCO3 precipitation (MICP) is an innovative and rapidly developing technology for sand solidification. The idea for this research project was built based on the concept of sustainable development and environmental protection. The specific material used for solidification was soluble calcium ions generated by the reaction of limestone waste, a kind of calcium-rich industrial waste from a quarry, and acetic acid. Using Ca(CH3COO)2 (prepared from limestone waste) as a calcium source resulted in a 31.87% lower MICP cost compared to using CaCl2. An unconfined compressive strength (UCS) test was conducted to characterize the macroscopic mechanical properties of bio-cured sand columns. The mineral composition and the microstructure of sand columns were examined by using X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM). After response surface optimization, the optimal conditions for the reaction of limestone and CH3COOH were determined, and the calcium acetate yield was up to 96.81%. The UCS of sand samples treated with limestone/acetic acid was 10.61% higher than that of samples treated with calcium chloride. This research confirmed the feasibility of cheap limestone waste and soluble calcium ions generated by acetic acid as a calcium source, instead of calcium chloride, for solidifying sand columns in the MICP process. Full article
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19 pages, 10481 KiB  
Article
Identification of Mutations Responsible for Improved Xylose Utilization in an Adapted Xylose Isomerase Expressing Saccharomyces cerevisiae Strain
by Ronald E. Hector, Jeffrey A. Mertens and Nancy N. Nichols
Fermentation 2022, 8(12), 669; https://doi.org/10.3390/fermentation8120669 - 23 Nov 2022
Cited by 1 | Viewed by 1441
Abstract
Economic conversion of biomass to biofuels and chemicals requires efficient and complete utilization of xylose. Saccharomyces cerevisiae strains engineered for xylose utilization are still considerably limited in their overall ability to metabolize xylose. In this study, we identified causative mutations resulting in improved [...] Read more.
Economic conversion of biomass to biofuels and chemicals requires efficient and complete utilization of xylose. Saccharomyces cerevisiae strains engineered for xylose utilization are still considerably limited in their overall ability to metabolize xylose. In this study, we identified causative mutations resulting in improved xylose fermentation of an adapted S. cerevisiae strain expressing codon-optimized xylose isomerase and xylulokinase genes from the rumen bacterium Prevotella ruminicola. Genome sequencing identified single-nucleotide polymorphisms in seven open reading frames. Tetrad analysis showed that mutations in both PBS2 and PHO13 genes were required for increased xylose utilization. Single deletion of either PBS2 or PHO13 did not improve xylose utilization in strains expressing the xylose isomerase pathway. Saccharomyces can also be engineered for xylose metabolism using the xylose reductase/xylitol dehydrogenase genes from Scheffersomyces stipitis. In strains expressing the xylose reductase pathway, single deletion of PHO13 did show a significant increase xylose utilization, and further improvement in growth and fermentation was seen when PBS2 was also deleted. These findings will extend the understanding of metabolic limitations for xylose utilization in S. cerevisiae as well as understanding of how they differ among strains engineered with two different xylose utilization pathways. Full article
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13 pages, 3302 KiB  
Article
Optimization of Culture Conditions and Wheat Bran Class Selection in the Production of Bacillus thuringiensis-Based Biopesticides
by Nancy Fayad, Joanna Abboud, Fatma Driss, Nicolas Louka and Mireille Kallassy Awad
Fermentation 2022, 8(12), 666; https://doi.org/10.3390/fermentation8120666 - 23 Nov 2022
Cited by 3 | Viewed by 1734
Abstract
Bacillus thuringiensis is the leading microbial-based biopesticide, thanks to its parasporal crystal proteins or δ-endotoxins, which are toxic to insect larvae upon ingestion. Once in the insect larvae midgut, the crystal is solubilized by the alkaline pH and the δ-endotoxins activated by proteolytic [...] Read more.
Bacillus thuringiensis is the leading microbial-based biopesticide, thanks to its parasporal crystal proteins or δ-endotoxins, which are toxic to insect larvae upon ingestion. Once in the insect larvae midgut, the crystal is solubilized by the alkaline pH and the δ-endotoxins activated by proteolytic cleavage. Thanks to its high efficiency as a biopesticide, several efforts have been made to enhance its growth and δ-endotoxins production, in various types of culture media. In this study, a culture medium based on wheat bran (WB), the by-product of cereal grain milling, was used to grow Bacillus thuringiensis and produce δ-endotoxins. Using the response surface methodology (RSM), the effects of three variables were evaluated: WB particles granulometry, their concentration, and their agitation in a 48-h shake-flask culture at 30 °C. Three response parameters were targeted: δ-endotoxins production, final culture pH, and dry-matter consumption. According to the RSM results, the optimum would be at 3.7 g WB/50 mL, with a granulometry above 680 μm and agitation between 170 and 270 rpm. This study is key to developing natural and cheap culture media that can be used at an industrial level for Bacillus thuringiensis-based biopesticides. Full article
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18 pages, 3209 KiB  
Article
Integrating Torrefaction of Pulp Industry Sludge with Anaerobic Digestion to Produce Biomethane and Volatile Fatty Acids: An Example of Industrial Symbiosis for Circular Bioeconomy
by Tharaka Rama Krishna C. Doddapaneni, Margareta Novian Cahyanti, Kaja Orupõld and Timo Kikas
Fermentation 2022, 8(9), 453; https://doi.org/10.3390/fermentation8090453 - 11 Sep 2022
Cited by 4 | Viewed by 1941
Abstract
Industrial symbiosis, which allows the sharing of resources between different industries, could help to improve the overall feasibility of bio-based chemicals production. In that regard, this study focused on integrating the torrefaction of pulp industry sludge with anaerobic digestion. More specifically, anaerobic digestion [...] Read more.
Industrial symbiosis, which allows the sharing of resources between different industries, could help to improve the overall feasibility of bio-based chemicals production. In that regard, this study focused on integrating the torrefaction of pulp industry sludge with anaerobic digestion. More specifically, anaerobic digestion (AD) of pulp sludge-derived torrefaction condensate (TC) was studied to evaluate the biomethane and volatile fatty acid (VFA) potential. The torrefaction condensate produced at 275 and 300 °C was used in AD. The volatile solid content (VS) was 6.69 and 9.01% for the condensate produced at 275 and 300 °C, respectively. The organic fraction of TC mainly contained acetic acid, 2-furanmethanol, and syringol. The methane yield was in the range of 481–772 mL/g VS for the mesophilic and 401–746 mL/g VS for the thermophilic process, respectively. The VFA yield was in the range of 1.1 to 3.4 g/g VS for mesophilic and from 1.5 to 4.7 g/g VS in thermophilic conditions, when methanogenesis was inhibited. Finally, pulp sludge TC is a feasible feedstock to produce platform chemicals like VFA. However, at higher substrate loading, signs of process inhibition were observed because of the relatively increasing concentration of microbial inhibitors Full article
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13 pages, 2558 KiB  
Article
Genomic and Transcriptional Characteristics of Strain Rum-meliibacillus sp. TYF-LIM-RU47 with an Aptitude of Directly Producing Acetoin from Lignocellulose
by Guoyang Feng, Xiaojun Fan, Yanna Liang, Chen Li, Junde Xing and Yongji He
Fermentation 2022, 8(8), 414; https://doi.org/10.3390/fermentation8080414 - 22 Aug 2022
Cited by 2 | Viewed by 1552
Abstract
Rummeliibacillus sp. TYF-LIM-RU47, isolated from the fermentation substrate of grain vinegar, could produce acetoin using a variety of carbon sources, including pentose, hexose and lignocellulose. The draft genome of TYF-LIM-RU47 was constructed and the genomic information revealed that TYF-LIM-RU47 contains genes related to [...] Read more.
Rummeliibacillus sp. TYF-LIM-RU47, isolated from the fermentation substrate of grain vinegar, could produce acetoin using a variety of carbon sources, including pentose, hexose and lignocellulose. The draft genome of TYF-LIM-RU47 was constructed and the genomic information revealed that TYF-LIM-RU47 contains genes related to starch and sucrose metabolism, pyruvate metabolism, the oxidative phosphorylation metabolic pathway and lignocellulosic metabolism. The acetoin anabolic pathway of TYF-LIM-RU47 has been deduced from the sequencing results, and acetoin is produced from α-acetolactate via decarboxylation and diacetyl reductase catalytic steps. The results of quantitative real-time PCR tests showed that the synthesis and degradation of acetoin had a dynamic balance in acetoin metabolism, and the transcription of the α-acetolactate synthase gene might exist to the extent of feedback regulation. This study can help researchers to better understand the bioinformation of thermophilic-lignocellulosic bacteria and the mechanisms of the acetoin biosynthesis pathway. Full article
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12 pages, 1651 KiB  
Article
Nitrification upon Nitrogen Starvation and Recovery: Effect of Stress Period, Substrate Concentration and pH on Ammonia Oxidizers’ Performance
by Leila Abbaszadeh, Eleni Koutra, Konstantina Tsigkou, Maria Gaspari, Panagiotis G. Kougias and Michael Kornaros
Fermentation 2022, 8(8), 387; https://doi.org/10.3390/fermentation8080387 - 13 Aug 2022
Cited by 4 | Viewed by 1916
Abstract
Nitrification has been widely applied in wastewater treatment, however gaining more insight into the nitrifiers’ physiology and stress response is necessary for the optimization of nutrient removal and design of advanced processes. Since nitrification initiates with ammonia oxidation performed by ammonia-oxidizing bacteria (AOB), [...] Read more.
Nitrification has been widely applied in wastewater treatment, however gaining more insight into the nitrifiers’ physiology and stress response is necessary for the optimization of nutrient removal and design of advanced processes. Since nitrification initiates with ammonia oxidation performed by ammonia-oxidizing bacteria (AOB), the purpose of this study was to investigate the effects of short-term ammonia starvation on nitrogen uptake and transformation efficiency, as well as the performance of starved nitrifiers under various initial substrate concentrations and pH values. Ammonium deprivation for 3 days resulted in fast ammonium/ammonia accumulation upon nitrogen availability, with a maximum uptake rate of 3.87 mmol gprotein−1 min−1. Furthermore, a delay in the production of nitrate was observed with increasing starvation periods, resulting in slower recovery and lower nitrification rate compared to non-starved cells. The maximum accumulation capacity observed was 8.51% (w/w) independently of the external nitrogen concentration, at a range of 250–750 mg N L−1, while pH significantly affected ammonia oxidizers’ response, with alkaline values enhancing nitrogen uptake. In total, ammonia accumulation after short-term starvation might serve as an important strategy that helps AOB restore their activity, while concurrently it could be applied in wastewater treatment for effective nitrogen removal and subsequent biomass utilization. Full article
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11 pages, 2902 KiB  
Article
Continuous Fermentation by Lactobacillus bulgaricus T15 Cells Immobilized in Cross-Linked F127 Hydrogels to Produce ᴅ-Lactic Acid
by Yongxin Guo, Gang Wang, Huan Chen, Sitong Zhang, Yanli Li, Mingzhu Guo, Juan Liu and Guang Chen
Fermentation 2022, 8(8), 360; https://doi.org/10.3390/fermentation8080360 - 28 Jul 2022
Cited by 2 | Viewed by 3494
Abstract
Lignocellulose biorefinery via continuous cell-recycle fermentation has long been recognized as a promising alternative technique for producing chemicals. ᴅ-lactic acid (D-LA) production by fermentation of corn stover by Lactobacillus bulgaricus was proven to be feasible by a previous study. However, the phenolic compounds [...] Read more.
Lignocellulose biorefinery via continuous cell-recycle fermentation has long been recognized as a promising alternative technique for producing chemicals. ᴅ-lactic acid (D-LA) production by fermentation of corn stover by Lactobacillus bulgaricus was proven to be feasible by a previous study. However, the phenolic compounds and the high glucose content in this substrate may inhibit cell growth. The immobilization of cells in polymer hydrogels can protect them from toxic compounds in the medium and improve fermentation efficiency. Here, we studied the production of D-LA by L. bulgaricus cells immobilized in cross-linkable F127 bis-polyurethane methacrylate (F127-BUM/T15). The Hencky stress and Hencky strain of F127-BUM/T15 was 159.11 KPa and 0.646 respectively. When immobilized and free-living cells were cultured in media containing 5-hydroxymethylfurfural, vanillin, or high glucose concentrations, the immobilized cells were more tolerant, produced higher D-LA yields, and had higher sugar-to-acid conversion ratios. After 100 days of fermentation, the total D-LA production via immobilized cells was 1982.97 ± 1.81 g with a yield of 2.68 ± 0.48 g/L h, which was higher than that of free cells (0.625 ± 0.28 g/L h). This study demonstrated that F127-BUM/T15 has excellent potential for application in the biorefinery industry. Full article
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15 pages, 1416 KiB  
Article
Hydrogen and Methane Production from Anaerobic Co-Digestion of Sorghum and Cow Manure: Effect of pH and Hydraulic Retention Time
by Margarita A. Dareioti, Konstantina Tsigkou, Aikaterini I. Vavouraki and Michael Kornaros
Fermentation 2022, 8(7), 304; https://doi.org/10.3390/fermentation8070304 - 27 Jun 2022
Cited by 12 | Viewed by 2166
Abstract
The need for alternative energy sources is constantly growing worldwide, while the focus has shifted to the valorization of biomass. The aim of the present study was to determine the optimal pH and hydraulic retention time (HRT) values for treating a mixture of [...] Read more.
The need for alternative energy sources is constantly growing worldwide, while the focus has shifted to the valorization of biomass. The aim of the present study was to determine the optimal pH and hydraulic retention time (HRT) values for treating a mixture of sorghum biomass solution with liquid cow manure (in a ratio 95:5 v/v) through anaerobic digestion, in a two-stage system. Batch tests were initially carried out for the investigation of the pH effect on bio-hydrogen and volatile fatty acids (VFA) production. The highest hydrogen yield of 0.92 mol H2/mol carbohydratesconsumed was obtained at pH 5.0, whereas the maximum degradation of carbohydrates and VFA productivity was observed at pH 6.0. Further investigation of the effect of HRT on hydrogen and methane production was carried out. The maximum yield of 1.68 mol H2/mol carbohydratesconsumed was observed at an HRT of 5 d, with H2 productivity of 0.13 L/LR·d. On the other hand, the highest CH4 production rate of 0.44 L/LR·d was achieved at an HRT of 25 d, with a methane yield of 295.3 mL/g VSadded, whereas at a reduced HRT of 20 d the process exhibited inhibition and/or overload, as indicated by an accumulation of VFAs and decline in CH4 productivity. Full article
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13 pages, 4120 KiB  
Article
Nutrition Component Adjustment of Distilled Dried Grain with Solubles via Aspergillus niger and Its Change about Dynamic Physiological Metabolism
by Weiwei Fan, Xuhui Huang, Kehan Liu, Yongping Xu, Bo Hu and Zhanyou Chi
Fermentation 2022, 8(6), 264; https://doi.org/10.3390/fermentation8060264 - 05 Jun 2022
Cited by 4 | Viewed by 1885
Abstract
The low fiber digestibility and unbalanced amino acids restricted the use of DDGS in swine diets. Key nutrition components dynamic monitoring and key regulatory pathways analysis were performed to find the rules of nutrition changes for DDGS fermented by Aspergillus niger. Cellulose [...] Read more.
The low fiber digestibility and unbalanced amino acids restricted the use of DDGS in swine diets. Key nutrition components dynamic monitoring and key regulatory pathways analysis were performed to find the rules of nutrition changes for DDGS fermented by Aspergillus niger. Cellulose and hemicellulose were reduced to 15.3% and 15.2%. 1,4-D-Xylobiose was decreased from 16.8 μg/mL to 0.2 μg/mL. Lys, Arg, and Thr were increased to 3.00%, 2.89%, and 4.40%, and met the requirements of pigs. The whole fermentation process was divided into three stages. Cellulose degradation and Lys and Arg synthesis occurred in the early stage, while Asp synthesis occurred in the last stage. α-Ketoglutarate was the key factor for Aspergillus niger degrading cellulose to synthesize Lys and Arg. The key active metabolic pathways that respond to the changes in nutrition were identified which preliminarily revealed the rules of nutrition adjustment of DDGS during fermentation with Aspergillus niger. Full article
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Review

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20 pages, 2320 KiB  
Review
Waste-Derived Renewable Hydrogen and Methane: Towards a Potential Energy Transition Solution
by Omprakash Sarkar, Jampala Annie Modestra, Ulrika Rova, Paul Christakopoulos and Leonidas Matsakas
Fermentation 2023, 9(4), 368; https://doi.org/10.3390/fermentation9040368 - 10 Apr 2023
Cited by 8 | Viewed by 3229
Abstract
Anaerobic digestion (AD) is an environmentally friendly process for recovering low-carbon energy from the breakdown of organic substrates. In recent years, AD has undergone a major paradigm shift, and now the technology is not only considered as a “waste treatment” method and is [...] Read more.
Anaerobic digestion (AD) is an environmentally friendly process for recovering low-carbon energy from the breakdown of organic substrates. In recent years, AD has undergone a major paradigm shift, and now the technology is not only considered as a “waste treatment” method and is instead viewed as a key enabler of the future “circular economy” with its potential for resource recovery (low-carbon energy, safe water, and nutrients). Currently, waste-derived biogas from AD is the most affordable and scalable source of renewable energy. Biomethane (upgraded biogas) can serve as a significant renewable and dispatchable energy source for combating the problem of global warming. Acidogenesis, an intermediate step of AD, can produce molecular hydrogen (H2) along with green chemicals/platform chemicals. The use of low-carbon hydrogen as a clean energy source is on the rise throughout the world, and is currently considered a potential alternative energy source that can contribute to the transition to a carbon-neutral future. In order to determine the future trade routes for hydrogen, nations are developing hydrogen policies, and various agreements. Hydrogen produced by biological routes has been found to be suitable due to its potential as a green energy source that is carbon neutral for the developing “Hydrogen Economy”. Recently, hydrogen blended with methane to a specific proportion and known as biohythane/hydrogen-enriched compressed natural gas (HCNG) has emerged as a promising clean fuel that can substantially contribute to an integrated net-zero energy system. This review provides an overview of the current state of fermentative hydrogen and methane production from biogenic waste/wastewater in a biorefinery approach and its utilization in the context of energy transition. The limitations and economic viability of the process, which are crucial challenges associated with biohydrogen/biomethane production, are discussed, along with its utilization. Full article
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34 pages, 1437 KiB  
Review
Lactic Acid for Green Chemical Industry: Recent Advances in and Future Prospects for Production Technology, Recovery, and Applications
by Jua Kim, Young-Min Kim, Veeranjaneya Reddy Lebaka and Young-Jung Wee
Fermentation 2022, 8(11), 609; https://doi.org/10.3390/fermentation8110609 - 06 Nov 2022
Cited by 24 | Viewed by 7248
Abstract
Lactic acid, an organic acid produced by numerous microorganisms, has many applications in the food, chemical, pharmaceutical, and polymer industries, with novel applications being developed particularly in the chemical industry. The lactic acid market has steadily grown with the introduction of novel and [...] Read more.
Lactic acid, an organic acid produced by numerous microorganisms, has many applications in the food, chemical, pharmaceutical, and polymer industries, with novel applications being developed particularly in the chemical industry. The lactic acid market has steadily grown with the introduction of novel and environmentally friendly products. Therefore, developing novel technologies for lactic acid production, with improved yield and reduced production costs, has become a major research goal. Utilization of inexpensive and renewable biomass is a major strategy for economically producing lactic acid. However, most lactic acid bacteria cannot directly utilize lignocellulosic biomass and require hydrolysis, which is costly. Immobilization techniques for large-scale production can enhance fermentation yield. Moreover, novel techniques, such as cell recycling systems and simultaneous saccharification, will enable microorganisms to produce lactic acid with increased concentration, yield, and productivity. Recently, genetic and metabolic engineering methods have been used for key solving problems, such as product inhibition, by-product formation, and suboptimal culture conditions, and for the effective use of cheap substrates. This review presents comprehensive insights into the most recent advances in the biological production of lactic acid from different substrates, bioprocess techniques for yield improvement, lactic acid purification, and applications of lactic acid for human welfare. Full article
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28 pages, 2243 KiB  
Review
A Review on the Production of C4 Platform Chemicals from Biochemical Conversion of Sugar Crop Processing Products and By-Products
by Gillian O. Bruni and Evan Terrell
Fermentation 2022, 8(5), 216; https://doi.org/10.3390/fermentation8050216 - 10 May 2022
Cited by 4 | Viewed by 3243
Abstract
The development and commercialization of sustainable chemicals from agricultural products and by-products is necessary for a circular economy built on renewable natural resources. Among the largest contributors to the final cost of a biomass conversion product is the cost of the initial biomass [...] Read more.
The development and commercialization of sustainable chemicals from agricultural products and by-products is necessary for a circular economy built on renewable natural resources. Among the largest contributors to the final cost of a biomass conversion product is the cost of the initial biomass feedstock, representing a significant challenge in effective biomass utilization. Another major challenge is in identifying the correct products for development, which must be able to satisfy the need for both low-cost, drop-in fossil fuel replacements and novel, high-value fine chemicals (and/or commodity chemicals). Both challenges can be met by utilizing wastes or by-products from biomass processing, which have very limited starting cost, to yield platform chemicals. Specifically, sugar crop processing (e.g., sugarcane, sugar beet) is a mature industry that produces high volumes of by-products with significant potential for valorization. This review focuses specifically on the production of acetoin (3-hydroxybutanone), 2,3-butanediol, and C4 dicarboxylic (succinic, malic, and fumaric) acids with emphasis on biochemical conversion and targeted upgrading of sugar crop products/by-products. These C4 compounds are easily derived from fermentations and can be converted into many different final products, including food, fragrance, and cosmetic additives, as well as sustainable biofuels and other chemicals. State-of-the-art literature pertaining to optimization strategies for microbial conversion of sugar crop byproducts to C4 chemicals (e.g., bagasse, molasses) is reviewed, along with potential routes for upgrading and valorization. Directions and opportunities for future research and industrial biotechnology development are discussed. Full article
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