Screening of a highly inhibitor-tolerant bacterial strain for 2,3-BDO and organic acid production from non-detoxified corncob acid hydrolysate

Mutation breeding of high-stress resistant strains for succinic acid production from corn straw

The production of succinic acid from corn stover is a promising and sustainable route; however, during the pretreatment stage, byproducts such as organic acids, furan-based compounds, and phenolic compounds generated from corn stover inhibit the microbial fermentation process. Selecting strains that are resistant to stress and utilizing nondetoxified corn stover hydrolysate as a feedstock for succinic acid production could be effective. In this study, A. succinogenes CICC11014 was selected as the original strain, and the stress-resistant strain A. succinogenes M4 was obtained by atmospheric and room temperature plasma (ARTP) mutagenesis and further screening. Compared to the original strain, A. succinogenes M4 exhibited a twofold increase in stress resistance and a 113% increase in succinic acid production when hydrolysate was used as the substrate. By conducting whole-genome resequencing of A. succinogenes M4 and comparing it with the original strain, four nonsynonymous gene mutations and two upstream regions with base losses were identified. KEY POINTS: • A high-stress-resistant strain A. succinogenes M4 was obtained by ARTP mutation •  The production of succinic acid increased by 113% • The mutated genes of A. succinogenes M4 were detected and analyzed.

Metabolic Engineering and Regulation of Diol Biosynthesis from Renewable Biomass in Escherichia coli

As bulk chemicals, diols have wide applications in many fields, such as clothing, biofuels, food, surfactant and cosmetics. The traditional chemical synthesis of diols consumes numerous non-renewable energy resources and leads to environmental pollution. Green biosynthesis has emerged as an alternative method to produce diols. Escherichia coli as an ideal microbial factory has been engineered to biosynthesize diols from carbon sources. Here, we comprehensively summarized the biosynthetic pathways of diols from renewable biomass in E. coli and discussed the metabolic-engineering strategies that could enhance the production of diols, including the optimization of biosynthetic pathways, improvement of cofactor supplementation, and reprogramming of the metabolic network. We then investigated the dynamic regulation by multiple control modules to balance the growth and production, so as to direct carbon sources for diol production. Finally, we proposed the challenges in the diol-biosynthesis process and suggested some potential methods to improve the diol-producing ability of the host.

Lignocellulose biomass bioconversion during composting: Mechanism of action of lignocellulase, pretreatment methods and future perspectives

Composting is a biodegradation and transformation process that converts lignocellulosic biomass into value-added products, such as humic substances (HSs). However, the recalcitrant nature of lignocellulose hinders the utilization of cellulose and hemicellulose, decreasing the bioconversion efficiency of lignocellulose. Pretreatment is an essential step to disrupt the structure of lignocellulosic biomass. Many pretreatment methods for composting may cause microbial inactivation and death. Thus, the pretreatment methods suitable for composting can promote the degradation and transformation of lignocellulosic biomass. Therefore, this review summarizes the pretreatment methods suitable for composting. Microbial consortium pretreatment, Fenton pretreatment and surfactant-assisted pretreatment for composting may improve the bioconversion process. Microbial consortium pretreatment is a cost-effective pretreatment method to enhance HSs yields during composting. On the other hand, the efficiency of enzyme production during composting is very important for the degradation of lignocellulose, whose action mechanism is unknown. Therefore, this review describes the mechanism of action of lignocellulase, the predominant microbes producing lignocellulase and their related genes. Finally, optimizing pretreatment conditions and increasing enzymatic hydrolysis to improve the quality of composts by controlling suitable microenvironmental factors and core target microbial activities as a research focus in the bioconversion of lignocellulose during composting in the future.

Lignocellulosic bio-refinery approach for microbial 2,3-Butanediol production

Bio-refinery approach using agricultural and industrial waste material as feedstock is becoming a preferred area of interest in biotechnology in the current decades. The reasons for this trend are mainly because of the declining petroleum resources, greenhouse gas emission risks and fluctuating market price of crude oil. Most chemicals synthesized petro chemically, can be produced using microbial biocatalysts. 2,3-Butanediol (BDO) is such an important platform bulk chemical with numerous industrial applications including as a fuel additive. Although microbial production of BDO is well studied, strategies that could successfully upgrade the current lab-scale researches to an industrial level have to be developed. This review presents an overview of the recent trends and developments in the microbial production of BDO from different lignocellulose biomass.