Application of chronological lifespan in the construction of Escherichia coli cell factories / 生物工程学报

Microbial cell factories capable of producing valuable chemicals from renewable feedstocks provide a promising alternative towards sustainability. However, environmental stress remarkably affects the performance of microbial cell factories. By extending the chronological lifespan of microbial cells, the performance of microbial cell factories can be greatly improved. Firstly, an evaluation system for chronological lifespan and semi-chronological lifespan was established based on the changes in survival rates. Secondly, the addition of anti-aging drugs such as cysteine, carnosine, aminoguanidine and glucosamine increased the chronological lifespan of E. coli by 80%, 80%, 50% and 120%, respectively. Finally, we demonstrated that extending the chronological lifespan of E. coli increased the yield of metabolites produced by E. coli cell factories with endogenous (lactic acid and pyruvic acid) or exogenous (malic acid) metabolic pathway by 30.0%, 25.0%, and 27.0%, respectively. The strategy of extending chronological lifespan of E. coli provides a potential approach for enhancing the performance of microbial cell factories.

Recent advances in enzymatic production of alpha-keto acids / 生物工程学报

Alpha-keto acid is a bifunctional organic compound containing both carboxyl and ketone groups, and widely applied in the industries of food, pharmaceutical and cosmetics. Based on the demand of eco-friendly process, safety and sustainable development, production of α-keto acids by enzymatic conversion technology has been paid more and more attention. In this article, we review the status of α-keto acids biosynthesis from three aspects: enzymatic screening, enzymatic modification and optimization of enzymatic conversion conditions. Meanwhile, we also indicate future research directions for further improving α-keto acids production.

Enzymatic production of arginine derivatives: a review / 生物工程学报

L-arginine (L-Arg) is an alkaline amino acid that possesses various function groups and acts as an important precursor for useful chemical synthesis. L-Arg derivatives are widely applied in pharmaceutical, food and cosmetic industries. Environment friendly and cost-effective production of L-Arg derivatives by enzymatic catalysis provides significant advantages over chemical synthesis and microbial fermentation. In this article, several typical L-Arg derivatives and their enzymatic production processes are highlighted. Furthermore, prospect is also addressed about enzymatic production of L-Arg derivatives.

Mutation and fermentation optimization of Bacillus amyloliquefaciens for acetoin production / 生物工程学报

As a platform chemical, acetoin has a great potential of application in medicine and food industries. In order to improve the efficiency of acetoin production, Bacillus amyloliquefaciens was treated by atmospheric and room temperature plasma and gamma rays. Two-round screening was adopted for obtaining positive mutants, and the best mutant B. amyloliquefaciens H-5 produced acetoin up to 68.2 g/L in shake flask. Then, culture conditions were optimized in 5-L fermentor to enhance acetoin production. Finally, 85.2 g/L acetoin was produced by B. amyloliquefaciens H-5, which was increased by 26.8% compared with that of the original strain B. amyloliquefaciens FMME088. These results indicated that the high-producing strain can be obtained efficiently by compound mutagenesis, which has a promising prospect for commercial scale process.

Manipulation of cofactor balance in microorganisms / 生物工程学报

Cofactor balance plays an important role in producing enzymes, pharmaceuticals and chemicals. To meet the demand of industrial production, microbes should maintain a maximal carbon flux towards target metabolites without fluctuations in cofactor. We reviewed the physiological function of cofactor and discussed detailed strategies to manipulate cofactor balance through biochemical engineering and metabolic engineering. Furthermore, we indicated future research needs to further regulate cofactor balance.

A method to increase the production of insulin precursor in Pichia pastoris / 生物工程学报

To improve the yield of insulin precursor (PI), we constructed a recombinant expression vector pPIC9K-PI and transformed it into Pichia pastoris GS115 using electroporation. After screening, a mutant strain CL012 with 12 copies was obtained on the YPDS plate containing 4.0 mg/mL G418. Then, the components of SNAREs (Soluble N-ethylmaleimide-sensitive factor attachment receptor proteins), SNC2 and SNC2-SSO2, were expressed in the strain CL012 to explore the effect of SNAREs on the yield of PI. In shake flask culture, the strains expressing SNC2 and SNC2-SSO2 yielded PI of 1.89 mg/L and 2.21 mg/L after methanol induction for 96 h, which were improved by 23.53% and 44.44% compared to that of strain CL012 (1.53 mg/L), respectively. Further, in a 5-L bioreactor, the yield of PI with strain CL012 was 53 mg/L for high-density fermentation, after 96 h of methanol induction, which was 34.64-fold higher than that of shake culture. The strains expressing SNC2 and SNC2-SSO2 yielded the PI of 64 mg/L and 78 mg/L, which were respectively increased by 20.75% and 47.17%, compared to that of strain CL012. This work indicated that SNAREs components promoted the secretion of PI to improve its heterologous expression in P. pastoris.