Advances in metabolic engineering for enhanced acetyl-CoA availability in yeast.

Acetyl-CoA is an intermediate metabolite in cellular central metabolism. It's a precursor for various valuable commercial products, including: terpenoids, fatty acids, and polyketides. With the advancement of metabolic and synthetic biology tools, microbial cell factories have been constructed for the efficient synthesis of acetyl-CoA and derivatives, with the Saccharomyces cerevisiae and Yarrowia lipolytica as two prominent chassis. This review summarized the recent developments in the biosynthetic pathways and metabolic engineering approaches for acetyl-CoA and its derivatives synthesis in these two yeasts. First, the metabolic routes involved in the biosynthesis of acetyl-CoA and derived products were outlined. Then, the advancements in metabolic engineering strategies for channeling acetyl-CoA toward the desired products were summarized, with particular emphasis on: enhancing metabolic flux in different organelles, refining precursor CoA synthesis, optimizing substrate utilization, and modifying protein acetylation level. Finally, future developments in advancing the metabolic engineering strategies for acetyl-CoA and related derivatives synthesis, including: reducing CO2 emissions, dynamically regulating metabolic pathways, and exploring the regulatory functions between acetyl-CoA levels and protein acetylation, are highlighted. This review provided new insights into regulating acetyl-CoA synthesis to create more effective microbial cell factories for bio-manufacturing.

Densification pretreatment triggers efficient methanogenic performance and robust microbial community during anaerobic digestion of corn stover.

The recalcitrant characteristics of lignocellulosic waste and difficulties in biomass transportation and storage severely limit bioenergy production through anaerobic digestion (AD). In this study, Densifying Lignocellulosic biomass with Chemicals (DLC) pretreatment was developed to address these issues. The results showed that DLC treated corn stover (CS) reached a cumulative methane yield of as high as 224.30 mL/g VS (Volatile Solids), which was 59.27 % higher than that of un-treated. The reduced scum formation in the reactor, increased components consumption of solid phase, and higher organic biodegradability of liquid phase in AD of DLC treated CS enhanced methane yield. Microbial analysis indicated that DLC pretreatment affected the bacterial and methanogenic community structure, and a co-network with Comamonas and Methanobacterium, etc. as hub microbes was constructed. This study proposed a promising technology that could be potentially applied to industrial AD of lignocellulosic biomass.

New insight into the impact of moisture content and pH on dissolved organic matter and microbial dynamics during cattle manure composting.

Composting is an effective way to treat agricultural waste, whereas inappropriate initial conditions could cause lower maturity and system instability. In this study, the dissolved organic matter dynamics and microbial community succession of cattle-manure composting were investigated under different initial moisture content (MC) and pH of raw material. The results indicated that the extended duration of thermophilic phase and the highest GI (germination index) value of final product were observed at matrix 60% MC and pH 8.5 (AT2 treatment). Microbial analysis showed that the succession of bacterial and fungal community was significantly influenced by total carbon (TN), pH and MC (P < 0.05). The relationship between microbial community and fluorescence regional integration (FRI) parameters demonstrated that Thermobifida (bacterial genus), Mycothermus and Thermomyces (fungal genera) were positively correlated with PV, n (the integral aera of Region V). This study could provide a potential strategy for large-scale industrial application of compost.

Effect of aeration rates on enzymatic activity and bacterial community succession during cattle manure composting.

In order to explore changes in microbial enzyme activity and bacterial community, a 60-day composting experiment was conducted using cattle manure and straw under aeration rates of 0.45, 0.68, and 0.90 L min-1 kg-1 fresh weight. High aeration rate increased the cellulase, urease, alkaline and acid phosphatase activities, but decreased that of invertase and catalase. Cellulase, alkaline phosphatase and catalase were the main enzymes that affected the composting process. Microbial analysis showed that high aeration rate increased the uniformity of bacterial community in thermophilic phase, but decreased that in mature phase. Different aeration rate affected the bacterial community structure and further influenced the relationship between enzyme and functional bacteria. Regulating the temperature, moisture content and EC in specific phases to affect bacterial community succession could provide guidance for improving maturity of composting.