Production of Microbial Secondary Metabolites from Organic Wastes and Investigation of Their Potential Applications

Prodigiosin is a red pigment produced by various microbial strains, of these, Serratia marcescens has been recorded as the major PG-producing strain. This microbial pigment has attracted much attention because it possesses potential applications in various fields. Thus, this active metabolite has been increasingly studied for bioproduction and investigated for its novel applications. Recently, several prodigiosin-related reviews were reported. These studies covered some aspects of the general physicochemical properties, pathway synthesis, production, and applications of prodigiosin in medicine. However, only a few works discussed the eco-friendly production of prodigiosin from organic wastes. Remarkably, the scaling-up of prodigiosin production and its potential applications in agriculture have rarely been reviewed or discussed. This review extensively presents and discusses the green biosynthesis, enhancement, and scaling-up of prodigiosin production from a wide range of organic byproducts/wastes using different methods of fermentation. Notably, this paper highlights the novel and promising applications of prodigiosin in agriculture via in vitro tests, greenhouse tests, and field studies. The action mechanisms related to some potential bioactivities and the toxicology studies of prodigiosin are also discussed. This review thus supplies scientific data for further research and the application of prodigiosin in the future. Full article

Among various organic wastes, shrimp shell powder (SSP) was the most suitable carbon/nitrogen source for producing antinematode compounds (ANCs) via Bacillus veleznesis RB.EK7 fermentation. The fermentation process for the enhancement of antinematode activity was investigated. B. veleznesis RB.EK7 produced the highest antinematode activity in the medium containing 0.8% SSP with an initial pH of 6.5–7.0, and fermentation was performed at 35–37 °C with a saking speed of 150 rpm for 72 h. Targeting ANCs were purified from the fermented culture broth and identified as thymine (1) and hexahydropyrrolo [1,2-a]pyrazine-1,4-dione (2) based on nuclear magnetic resonance (NMR) and mass spectra analysis and were compared to those of the reported compounds. Notably, for the first time, these compounds were found as novel ANCs. Thymine (1) demonstrated a potential nematicidal effect with near 100% mortality of second-stage juvenile (J2) nematodes and anti-egg hatching effects of 70.1%, while hexahydropyrrolo [1,2-a]pyrazine-1,4-dione showed moderate antinematode activities with 64.2% mortality of J2 nematodes and anti-egg hatching effects of 57.9%. The docking study coupled with experimental enzyme inhibition results indicated that the potent nematicidal effect of these compounds may be possibly due to the inhibition of the targeting enzyme acetylcholinesterase. The data of this study suggest that SSP can be potentially reused for the eco-friendly production of ANCs for the management of black pepper nematodes. Full article