Food is the foundation of agricultural production, and although China is the world's largest food producer, traditional agriculture requires large amounts of land. Countries are developing large-scale synthetic starch and protein technologies, and our scientists have recently made important progress in this area, and have reduced production costs significantly.

According to the Chinese Academy of Sciences, the Center for In Vitro Synthetic Biology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, in collaboration with the Institute of Biotechnology, Chinese Academy of Agricultural SciencesNew advances in the efficient synthesis of starch and microbial protein using corn stover as substrate.

In the first stage, the research team focused on straw to starch, according to the idea of cellulose hydrolysis, cellulose disaccharide phosphorylation and polymerization, designed and created a multi-enzyme molecular machine for straw to starch, reconstructed the in vitro artificial metabolic transformation pathway, broke through the key problem of cellulose β-1,4 glycosidic bond directed rearrangement to starch a-1,4 glycosidic bond transformation, etc., and successfully realized the conversion and synthesis from cellulose to starch.

However, this route still faces the problems of low substrate energy utilization efficiency, slow conversion speed and high cost in the biotransformation process, and is far from industrial application.

The research team has been working on the route for five years to improve its economic feasibility, and has designed and modified the core components of the multi-enzyme molecular machine and optimized the synthesis line, which has significantly improved the efficiency of straw to starch conversion and laid the foundation for promoting industrial application.

Schematic diagram of a new method for converting straw into starch and microbial protein

By systematically designing and modifying recombinant enzyme-expressing strains, selecting inexpensive inorganic nitrogen sources to reduce media costs, and developing high-density microbial cultures, the research teamReduce the production cost of recombinant enzymes such as cellobiose phosphorylase and a-glucan phosphorylase to 250 RMB/kg.

Secondly, by preparing pretreated straw biomass or solid pretreated cellulose as an affinity adsorption medium, simple and efficient selective adsorption of endoglucanase and exoglucanase in cellulase, and efficient removal of β-glucosidase from cellulase, the efficient targeted degradation of straw cellulose was achieved, and the efficiency of cellulose hydrolysis was greatly improved.

Again, the research team immobilized cellobiose phosphorylase and a-glucan phosphorylase on the surface of Saccharomyces cerevisiae to effectively utilize glucose, an intermediate product of cellulose hydrolysis, to relieve the inhibitory effect of glucose on cellulase, enhance cellulase hydrolysis capacity, and enable a significant reduction in cellulase dosage.

Finally, the glucose produced by cellulose hydrolysis was utilized by aerobic fermentation with yeast, which achieved microbial protein co-production and significantly reduced the overall cost of the conversion route.