Heterogeneous Strategies For Selective Conversion of Lignocellulosic Polysaccharides

Lignocellulosic biomass is the most abundant renewable carbon resource on earth, for which many efforts have been made to convert it using various chemocatalytic processes. Heterogeneously chemocatalytic conversion conducted based on reusable solid catalysts is the process with the greatest potential studied presently. This review provides insights into the representative achievements in the research area of heterogeneous chemical catalysis technologies for the production of value-added chemicals from lignocellulosic polysaccharides (cellulose and hemicellulose). Popular approaches for the conversion of lignocellulosic polysaccharides into chemicals, including hydrolyzation (glucose, xylose and arabinose), dehydration (5-hydroxymethylfurfuran, furfural and levulinic acid), hydrogenation/hydrogenolysis (sorbitol, mannitol, xylitol, 1,2-propylene glycol, ethlyene glycol and ethanol), selective oxidation (gluconic acid and lactic acid), have been comprehensively reviewed. However, technological barriers still exist, which have to be overcome to further integrate hydrolysis with the refinery processes based on multifunctional solid catalysts, and convert ligncellulosic polysaccharides into value-added fine chemicals. In general, the approaches and technologies are discussed and critically evaluated in terms of the possibilities and potential for further industrial implementation.

Biocatalytic C-C Bond Formation for One Carbon Resource Utilization

The carbon-carbon bond formation has always been one of the most important reactions in C1 resource utilization. Compared to traditional organic synthesis methods, biocatalytic C-C bond formation offers a green and potent alternative for C1 transformation. In recent years, with the development of synthetic biology, more and more carboxylases and C-C ligases have been mined and designed for the C1 transformation in vitro and C1 assimilation in vivo. This article presents an overview of C-C bond formation in biocatalytic C1 resource utilization is first provided. Sets of newly mined and designed carboxylases and ligases capable of catalyzing C-C bond formation for the transformation of CO2, formaldehyde, CO, and formate are then reviewed, and their catalytic mechanisms are discussed. Finally, the current advances and the future perspectives for the development of catalysts for C1 resource utilization are provided.

Resource plasticity-driven carbon-nitrogen budgeting enables specialization and division of labor in a clonal community

Previously, we found that in glucose-limited Saccharomyces cerevisiae colonies, metabolic constraints drive cells into groups exhibiting gluconeogenic or glycolytic states. In that study, threshold amounts of trehalose - a limiting, produced carbon-resource, controls the emergence and self-organization of cells exhibiting the glycolytic state, serving as a carbon source that fuels glycolysis (Varahan et al., 2019). We now discover that the plasticity of use of a non-limiting resource, aspartate, controls both resource production and the emergence of heterogeneous cell states, based on differential metabolic budgeting. In gluconeogenic cells, aspartate is a carbon source for trehalose production, while in glycolytic cells using trehalose for carbon, aspartate is predominantly a nitrogen source for nucleotide synthesis. This metabolic plasticity of aspartate enables carbon-nitrogen budgeting, thereby driving the biochemical self-organization of distinct cell states. Through this organization, cells in each state exhibit true division of labor, providing growth/survival advantages for the whole community.

Production the industrial levels of bioethanol from glycerol by engineered yeast “Bioethanol-4th generation”

Besides the pledges for expanding uses of biofuels to sustain the humanosphere, abruptly massive needs emerged for sanitizers with turns COVID-19 to a pandemic. Therefore, ethanol is topping the social-demanding, although the three generations of production, from molasses/starch, lignocelluloses, and algae. Owing to the limited-availability of fermentable sugars from these resources, we addressed glycerol as a fourth bio-based carbon resource from biodiesel, soap, and fatty acid industries, which considers as a non-applicable source for bioethanol production. Here, we show the full strategy to generate efficient glycerol fermenting yeast by innovative rewriting the oxidation of cytosolic nicotinamide-adenine-dinucleotide (NADH) by O2-dependent dynamic shuttle while abolishing glycerol biosynthesis route. Besides, imposing a vigorous glycerol-oxidative pathway, the engineered strain demonstrated a breakthrough in conversion efficiency (up to 98%). Its capacity extending to produce up to 90g /l ethanol and > 2 g 1-1 h-1, which promoting the industrial view. Visionary metabolic engineering here provides horizons for further tremendous economic and health benefits with assuring for its enhancing for the other scenarios of biorefineries.SummaryEfficiently fermenting glycerol in yeast was developed by comprehensive engineering the glycerol pathways and rewriting NADH pathways.