Provided is an acid-tolerant yeast cell, a method of producing an organic acid by using the yeast cell, and a method of producing the yeast cell resistant to acid.

The present invention discloses a DL-alanine-producing genetically engineered strain, as well as a method of construction and use thereof, and pertains to the field of bioengineering. According to the present invention, through enhancing the glycolysis pathway or/and introducing thermostable alanine dehydrogenase, a genetically engineered strain capable of high-yield production of alanine at 42 C. to 55 C. This strain can be used in a two-step method for producing racemic DL-alanine, which includes fermentation and subsequent addition of microbial alanine racemase. Through inactivating or deleting alanine racemase genes in this strain and then separately introducing overexpressed alanine racemase gene(s), a genetically engineered strain capable of producing racemic DL-alanine using a direct fermentation method can be constructed. When the original strain possesses a lactate synthesis pathway, blocking this lactate synthesis pathway in both the genetically engineered strains can additionally augment the proportion of a pyruvate synthesis pathway.

This disclosure provides methods and genetically engineered strains of Vibrio natriegens, specifically developed for the bio-based production of succinate. Capitalizing on the rapid growth kinetics and highly efficient carbon metabolism of V. natriegens, this disclosure provides an environmentally friendly, scalable, and cost-effective alternative to traditional petrochemical methods for succinate production.

Provided are a method for constructing a lactic acid-producing strain, a lactic acid-producing strain and use thereof. The method for constructing lactic acid-producing strains is characterized by genetically engineering a starting strain to increase lactic acid production, wherein the engineering includes: 1) introducing a lactic acid synthesis pathway; 2) optimizing the lactic acid synthesis pathway; and 3) inhibiting by-product synthesis pathways.

The present invention discloses an L-alanine-producing genetically engineered strain, as well as a method of construction and use thereof, and pertains to the field of bioengineering. According to the present invention, through enhancing the glycolysis pathway or/and introducing a gene for thermostable alanine dehydrogenase, a genetically engineered strain capable of high-yield production of alanine under a high temperature condition of 42 C. to 55 C. can be constructed. Moreover, through knocking out alanine racemase genes, optical purity of L-alanine can be significantly increased. When the original strain possesses a lactate synthesis pathway, blocking this lactate synthesis pathway can augment the proportion of a pyruvate synthesis pathway, resulting in an additionally increased yield of L-alanine. The present invention overcomes the problems of fermentation at a low temperature, high cost and the like, which arise from the use of conventional L-alanine production techniques, enables production of L-alanine by fermentation at a high temperature of 42 C. to 55 C. with a yield of 95 g/L or higher, and is of high value to industrial application.

The present invention discloses a bacterium and an obtaining method and application thereof. The bacterium has a property of coproducing 1,3-propanediol and D-lactic acid. Further, the bacterium is Klebsiella oxytoca, including Klebsiella oxytoca PDL-5 CCTCC M 2016185. The obtaining method of the bacterium may be to obtain the bacterium by directly screening wild bacteria that satisfy conditions from the environment or performing gene engineering modification to wild bacteria. The present invention has the advantages that the bacteria can coproduce 1,3-propanediol and D-lactic acid through fermentation, the molar conversion rate and the concentration of the two products are very high, the types of byproducts are few, the concentration is low, the product extraction process is simplified, the high-efficiency biological production of 1,3-propanediol and D-lactic acid can be realized, and the industrial application prospect is very great.