Fermentation

Research

16 pages, 5217 KiB

Open AccessArticle

Ethanol Production from a Mixture of Waste Tissue Paper and Food Waste through Saccharification and Mixed-Culture Fermentation

by Hongzhi Ma, Yueyao Wang, Pin Lv, Jun Zhou, Ming Gao, Dayi Qian, Bo Song and Qunhui Wang

Fermentation 2024, 10(4), 194; https://doi.org/10.3390/fermentation10040194 - 02 Apr 2024

Viewed by 770

Abstract

This study focused on the co-fermentation of food waste and tissue paper to produce ethanol, which will eliminate the need for additional nitrogen sources and nutrients, thereby reducing production costs. In response to the inhibitory effect of the high concentrations of glucose present [...] Read more.

This study focused on the co-fermentation of food waste and tissue paper to produce ethanol, which will eliminate the need for additional nitrogen sources and nutrients, thereby reducing production costs. In response to the inhibitory effect of the high concentrations of glucose present in mixed-substrate hydrolysates on xylose fermentation, a co-fermentation process using Saccharomyces cerevisiae and Candida shehatae was proposed. This approach reduced the fermentation time by 24 h, increased the xylose utilization rate to 88%, and improved the ethanol yield from 41% to 46.5%. The impact of external conditions and corresponding optimization were also analyzed in this process. The optimum conditions were a 1:3 ratio of Saccharomyces cerevisiae to Candida shehatae, a pH of 5, and shaking at 150 r/min, and by employing dynamic temperature control, the ethanol production was increased to 21.98 g/L. Compared to conventional processes that only use Saccharomyces cerevisiae, this method enhanced the ethanol yield from 41% to 49%. Full article

(This article belongs to the Special Issue Anaerobic Digestion: Waste to Energy)

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14 pages, 2786 KiB

Open AccessArticle

Acclimation of Microbial Consortia to Ammonia and Salt in Methane Fermentation

by Takahisa Tajima, Shiina Kawaguchi, Tomoka Matsutani, Akiko Hida and Junichi Kato

Fermentation 2024, 10(2), 98; https://doi.org/10.3390/fermentation10020098 - 07 Feb 2024

Viewed by 1210

Abstract

As methane fermentation is inhibited by ammonia derived from organic waste, anaerobic microbial communities tolerant to enriched wastewater with high concentrations of ammonia and salt must be obtained for methane fermentation. Therefore, acclimation cultures were prepared in bottles for 60–80 weeks with artificial [...] Read more.

As methane fermentation is inhibited by ammonia derived from organic waste, anaerobic microbial communities tolerant to enriched wastewater with high concentrations of ammonia and salt must be obtained for methane fermentation. Therefore, acclimation cultures were prepared in bottles for 60–80 weeks with artificial wastewater medium added every 2 weeks, using three types of sludge from wastewater treatment plants in food factories. These cultures were maintained without substantially decreasing methanogenesis and gradually increasing NH₄-N and salt concentrations to 5 and 34 g/L, respectively, via the accumulation of ammonia and salt through anaerobic digestion and direct addition. The culture did not show the severe inhibition of methanogenesis or the accumulation of volatile fatty acids (VFAs) such as acetic and propionic acids. The analysis of bacterial consortia in the acclimated sludge based on the 16S rRNA sequence showed that hydrogenotrophic methanogenic bacteria of the genus Methanoculleus were dominant among archaea, whereas bacteria from the orders Clostridiales and Bacteroidales were dominant among eubacteria. Further, VFA-assimilating bacteria, including synthetic acetate-oxidizing bacteria coupled with hydrogenotrophic Methanoculleus to convert methane from acetate, were present to prevent the excessive accumulation of VFAs in the acclimation culture. The proposed acclimation process can enhance the anaerobic digestion of wastewater for methane production. Full article

(This article belongs to the Special Issue Anaerobic Digestion: Waste to Energy)

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17 pages, 12426 KiB

Open AccessArticle

Effects of One-Step Abrupt Temperature Change on Anaerobic Co-Digestion of Kitchen Waste with Dewatered Sludge

by Weijie Hu, Youfei Zhou, Hong Zhu and Tianfeng Wang

Fermentation 2024, 10(1), 5; https://doi.org/10.3390/fermentation10010005 (registering DOI) - 20 Dec 2023

Viewed by 1081

Abstract

The operating temperature of anaerobic digesters should be adjusted to adapt to seasonal variations in environmental temperature and the composition of organic solid waste. This study investigated the effects of one-step abrupt temperature changes (from mesophilic to thermophilic temperature, M–T, and from thermophilic [...] Read more.

The operating temperature of anaerobic digesters should be adjusted to adapt to seasonal variations in environmental temperature and the composition of organic solid waste. This study investigated the effects of one-step abrupt temperature changes (from mesophilic to thermophilic temperature, M–T, and from thermophilic to mesophilic temperature, T–M) and the inoculation ratio on methane yield and microbial diversity during the anaerobic co-digestion of kitchen waste with dewatered sludge. The results showed that the cumulative methane yield (CMY) level resulting from thermophilic control and the M–T digesters was greater than that resulting from mesophilic control and the T–M digesters. The CMF of M–T digesters increased, whereas the CMY of T–M digesters gradually decreased with an increase in the inoculation ratio. The maximal CMY was 385.1 mL/g-VSS_added, which corresponded to an M–T digester with a 5% inoculation ratio. In the later stage of anaerobic digestion, the bacterial community of T–M was more diverse than that of M–T, but the archaeal community of M–T was more diverse than that of T–M. The one-step temperature change from thermophilic to mesophilic temperature was more stable than that from mesophilic to thermophilic temperature. Full article

(This article belongs to the Special Issue Anaerobic Digestion: Waste to Energy)

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13 pages, 1879 KiB

Open AccessArticle

Effect of Photo Irradiation on the Anaerobic Digestion of Waste Sewage Sludge-Reduced Methane and Hydrogen Sulfide Productions

by Shotaro Toya, Shunsuke Iriguchi, Kohei Yamaguchi and Toshinari Maeda

Fermentation 2023, 9(11), 943; https://doi.org/10.3390/fermentation9110943 - 30 Oct 2023

Cited by 1 | Viewed by 998

Abstract

Since a large amount of sewage sludge (WSS) is generated daily, exploring effective methods for utilizing WSS is necessary. Although a photo-fermentation system sometimes alters the characteristics of microbial functions, there have been no attempts to perform photo-fermentation using WSS, which is regularly [...] Read more.

Since a large amount of sewage sludge (WSS) is generated daily, exploring effective methods for utilizing WSS is necessary. Although a photo-fermentation system sometimes alters the characteristics of microbial functions, there have been no attempts to perform photo-fermentation using WSS, which is regularly treated via dark fermentation. In this study, the effect of photo-fermentation (photo-irradiation) on anaerobic digestion using WSS was revealed. Photo-irradiation during the anaerobic digestion of WSS significantly reduced the amount of methane and hydrogen sulfide. Methane production was also reduced 5.6-fold at 13 days under light conditions, whereas hydrogen sulfide was consumed almost completely at 6 days. However, it was shown that the activity of sulfate-reducing bacteria in WSS under light treatment increased. Photo-irradiation also stimulated the growth of green sulfur bacteria and induced anoxygenic photosynthesis, via which process the fermented samples turned green in a manner that was correlated with their consumption of hydrogen sulfide. The production of organic acids was lowered in the samples that were irradiated using light. Finally, dark/light switching fermentation was only able to reduce hydrogen sulfide while methane production remained the same. The amounts of methane and hydrogen sulfide were 35 mmol/g VS, and they were undetected at 58 days in photo-irradiated samples compared to the control samples that produced 37 mmol/g VS of methane and 15 ppm/g VS of hydrogen sulfide. Full article

(This article belongs to the Special Issue Anaerobic Digestion: Waste to Energy)

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16 pages, 2718 KiB

Open AccessArticle

High-Titer Bioethanol Production from Steam-Exploded Corn Stover Using an Engineering Saccharomyces cerevisiae Strain with High Inhibitor Tolerance

by Yilu Wu, Changsheng Su, Gege Zhang, Zicheng Liao, Jieyi Wen, Yankun Wang, Yongjie Jiang, Changwei Zhang and Di Cai

Fermentation 2023, 9(10), 906; https://doi.org/10.3390/fermentation9100906 - 13 Oct 2023

Cited by 2 | Viewed by 1662

Abstract

Bioethanol is an important biofuel which can be produced from the abundant low-value lignocelluloses. However, the highly toxic inhibitory compounds formed in the hydrolysate and the ineffective utilization of xylose as a co-substrate are the primarily bottlenecks that hinder the commercialization of lignocellulosic [...] Read more.

Bioethanol is an important biofuel which can be produced from the abundant low-value lignocelluloses. However, the highly toxic inhibitory compounds formed in the hydrolysate and the ineffective utilization of xylose as a co-substrate are the primarily bottlenecks that hinder the commercialization of lignocellulosic bioethanol. In this study, aiming to properly solve the above obstacles, an engineered Saccharomyces cerevisiae strain was constructed by introducing the xylose reductase (XR)–xylitol dehydrogenase (XDH) pathway, overexpressing the non-oxidized pentose phosphate pathway, and deleting aldose reductase GRE3 and alkaline phosphatase PHO13 using a GTR-CRISPR system, followed by adaptive laboratory evolution (ALE). After screening, the isolated S. cerevisiae YL13-2 mutant was capable of robust xylose-utilizing, and exhibited high tolerance to the inhibitors in undetoxified steam-exploded corn stover hydrolysate (SECSH). An ethanol concentration of 22.96 g/L with a yield of 0.454 g/g can be obtained at the end of batch fermentation when using SECSH as substrate without nutrient supplementation. Moreover, aiming to simplify the downstream process and reduce the energy required in bioethanol production, fermentation using fed-batch hydrolyzed SECSH containing higher titer sugars with a YL13-2 strain was also investigated. As expect, a higher concentration of ethanol (51.12 g/L) was received, with an average productivity and yield of 0.71 g/L h and 0.436 g/g, respectively. The findings of this research provide an effective method for the production of bioethanol from lignocellulose, and could be used in large-scale applications in future works. Full article

(This article belongs to the Special Issue Anaerobic Digestion: Waste to Energy)

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18 pages, 4554 KiB

Open AccessArticle

Impact of Mechanical Stirring and Percolate Recirculation on the Performances of Dry Anaerobic Digestion

by Zhikai Zhang, Shengqiang Chang, Shengyong Zhao, Peng Liu, Yanan Qian and Wangliang Li

Fermentation 2023, 9(9), 848; https://doi.org/10.3390/fermentation9090848 - 15 Sep 2023

Viewed by 1086

Abstract

Dry anaerobic digestion (DAD) is an attractive method for simultaneous organic waste disposal and bioenergy recovery. DAD has the problems of low methane yields, low reaction rates, and easy inhibition due to its limited mass transfer and heat transfer. In this work, two [...] Read more.

Dry anaerobic digestion (DAD) is an attractive method for simultaneous organic waste disposal and bioenergy recovery. DAD has the problems of low methane yields, low reaction rates, and easy inhibition due to its limited mass transfer and heat transfer. In this work, two methods of mechanical stirring and percolate recirculation were compared regarding their capacities of improving the mass transfer and enhancing the performances of DAD in batch experiments with sorghum stalks as a substrate. The cumulative biogas yield and system stability were investigated when the stirring linear velocity was 0 cm/s, 22 cm/s, 44 cm/s, 66 cm/s, and 88 cm/s. When the stirring linear velocity was 88 cm/s, the cumulative biogas yield and methane content were highest. The computational fluid dynamics (CFD) simulation indicated that the shearing force near the stirring shaft was largest. When the linear velocity of the stirring paddle was 88 cm/s, the shearing force at a radial distance close to center was about −140 N/m². When the ratio of the material stacking height to the reactor diameter (H/D) was 3:2, the AD showed the best performance. A higher material stacking height promoted the contact between the microorganisms and the substrate and enhanced the biogas production. By combining percolate recirculation and mechanical stirring, the cumulative biogas yield increased by 28% compared with the static DAD process because of the promotion of mass transfer in the DAD. Full article

(This article belongs to the Special Issue Anaerobic Digestion: Waste to Energy)

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13 pages, 1488 KiB

Open AccessArticle

Zero-Valent Iron and Activated Carbon Coupled to Enhance Anaerobic Digestion of Food Waste: Alleviating Acid Inhibition at High Loads

by Shuang Zhang, Pan Zhao, Ming Gao, Chuanfu Wu, Qunhui Wang and Xiaohong Sun

Fermentation 2023, 9(9), 818; https://doi.org/10.3390/fermentation9090818 - 07 Sep 2023

Viewed by 756

Abstract

Anaerobic digestion (AD) has the advantages of utilizing complex substrates and producing renewable energy and is currently one of the mainstream technologies for food waste (FW) resourcing. However, at high organic loads and low inoculum-to-substrate ratios (ISRs), AD with FW as substrate is [...] Read more.

Anaerobic digestion (AD) has the advantages of utilizing complex substrates and producing renewable energy and is currently one of the mainstream technologies for food waste (FW) resourcing. However, at high organic loads and low inoculum-to-substrate ratios (ISRs), AD with FW as substrate is prone to acid accumulation, resulting in a drastic decrease in gas production and system collapse. This study investigated the effect of the coupled addition of zero-valent iron (ZVI) and activated carbon (AC) on the AD of FW at three low ISRs of 0.715, 0.625, and 0.5. The results showed that the control group acidified and stopped producing biogas when the ISR decreased to 0.625 and 0.5, but ZVI coupled with AC alleviated the acidification and increased the cumulative biogas yield. Especially at ISR = 0.5, the cumulative biogas yield for the ZVI + AC group was 31.5%, 99.5%, and 11.43 times higher than that of the ZVI, AC, and control groups, respectively. ZVI coupled with AC also increased the degradation of volatile fatty acids (70.5–84.4%) and soluble chemical oxygen demand (50.0–72.9%) while decreasing propionate concentration and improving the stability of the AD system. COD mass balance analyses indicated that the coupled addition of ZVI and AC promoted the conversion of particulate organic matter to soluble organic matter and increased the conversion of carbon sources to methane. Full article

(This article belongs to the Special Issue Anaerobic Digestion: Waste to Energy)

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16 pages, 2498 KiB

Open AccessEditor’s ChoiceArticle

Effects of Temperature Shifts on Microbial Communities and Biogas Production: An In-Depth Comparison

by Gede Adi Wiguna Sudiartha, Tsuyoshi Imai, Chonticha Mamimin and Alissara Reungsang

Fermentation 2023, 9(7), 642; https://doi.org/10.3390/fermentation9070642 - 08 Jul 2023

Cited by 5 | Viewed by 1489

Abstract

Temperature plays a significant role in anaerobic digestion (AD) as it affects the microbial communities and ultimately controls the efficiency of the process. Few studies have looked at temperature-adjusted AD, but it is unclear how the temperature shifts affect biogas production and the [...] Read more.

Temperature plays a significant role in anaerobic digestion (AD) as it affects the microbial communities and ultimately controls the efficiency of the process. Few studies have looked at temperature-adjusted AD, but it is unclear how the temperature shifts affect biogas production and the dynamics of microorganisms involved in methanogenesis. This study tested two temperature shift scenarios in fed-batch mode using anaerobically digested sewage sludge and glucose-based substrate. The first scenario was acclimatized to upshifting temperatures from 42 °C to 48 °C while the second was acclimatized to downshifting temperatures from 55 °C to 45 °C. Both temperature shift scenarios resulted in a decrease in biogas production, especially at 45 °C. The upshifted scenario experienced a maximum decrease of 83%, and the downshifted scenario experienced a 16–33% decrease in methane production. Next-generation 16S rRNA sequencing revealed the domination of Methanoculleus in the upshifted scenario. However, a low correlation between the number of Methanoculleus and the other hydrogenotrophic methanogens to biogas production indicates inhibition in the hydrogenotrophic pathway. The downshifted scenario showed better biogas production due to the substantial domination of acetoclastic Methanosaeta and the low abundance of sulfate-reducing bacteria. Hence, the temperature shift affects the microbial communities, significantly affecting biogas production performance. Full article

(This article belongs to the Special Issue Anaerobic Digestion: Waste to Energy)

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