Increasing ethanol titer and yield in a gpd1Δ gpd2Δ strain by simultaneous overexpression of GLT1 and STL1 in Saccharomyces cerevisiae

CRISPR-Cas9 Approach Constructed Engineered Saccharomyces cerevisiae with the Deletion of GPD2, FPS1, and ADH2 to Enhance the Production of Ethanol

Bioethanol plays an important value in renewable liquid fuel. The excessive accumulation of glycerol and organic acids caused the decrease of ethanol content in the process of industrial ethanol production. In this study, the CRISPR-Cas9 approach was used to construct S. cerevisiae engineering strains by the deletion of GPD2, FPS1, and ADH2 for the improvement of ethanol production. RNA sequencing and transcriptome analysis were used to investigate the effect of gene deletion on gene expression. The results indicated that engineered S. cerevisiae SCGFA by the simultaneous deletion of GPD2, FPS1, and ADH2 produced 23.1 g/L ethanol, which increased by 0.18% in comparison with the wild-type strain with 50 g/L of glucose as substrate. SCGFA strain exhibited the ethanol conversion rate of 0.462 g per g of glucose. In addition, the contents of glycerol, lactic acid, acetic acid, and succinic acid in SCGFA decreased by 22.7, 12.7, 8.1, 19.9, and 20.7% compared with the wild-type strain, respectively. The up-regulated gene enrichment showed glycolysis, fatty acid, and carbon metabolism could affect the ethanol production of SCGFA according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Therefore, the engineering strain SCGFA had great potential in the production of bioethanol.

Cell Factory Engineering

Rational approaches to modifying cells to make molecules of interest are of substantial economic and scientific interest. Most of these efforts aim at the production of native metabolites, expression of heterologous biosynthetic pathways, or protein expression. Reviews of these topics have largely focused on individual strategies or cell types, but collectively they fall under the broad umbrella of a growing field known as cell factory engineering. Here we condense >130 reviews and key studies in the art into a meta-review of cell factory engineering. We identified 33 generic strategies in the field, all applicable to multiple types of cells and products, and proven successful in multiple major cell types. These apply to three major categories: production of native metabolites and/or bioactives, heterologous expression of biosynthetic pathways, and protein expression. This meta-review provides general strategy guides for the broad range of applications of rational engineering of cell factories.

Ethanol fermentation from non-detoxified lignocellulose hydrolysate by a multi-stress tolerant yeast Candida glycerinogenes mutant

The aim of this work was to study ethanol fermentation properties of the robust mutant Candida glycerinogenes UG21 from non-detoxified lignocellulose hydrolysate. C. glycerinogenes UG21 with high tolerance to elevated temperature, acetic acid, and furfural was obtained and applied in lignocellulose-based ethanol production. C. glycerinogenes UG21 exhibited highly-efficient degradation ability to furfural. High levels of acetic acid and furfural inhibited cell growths and ethanol production of Saccharomyces cerevisiae ZWA46 and industrial Angel yeast but had a slight impact on biomass and ethanol titer of C. glycerinogenes UG21. Using non-detoxified sugarcane bagasse hydrolysate, C. glycerinogenes UG21 reached 1.24 g/L/h of ethanol productivity at 40 °C but ethanol production of S. cerevisiae ZWA46 and Angel yeast was inhibited. Further, C. glycerinogenes UG-21 exhibited 2.42-fold and 1.58-fold higher productivity than S. cerevisiae ZWA46 and Angel yeast under low-toxicity hydrolysate. Therefore, C. glycerinogenes UG-21 could be an excellent candidate for low-cost lignocelluloses ethanol production.

Recent trends in bioethanol production from food processing byproducts

The widespread use of corn starch and sugarcane as sources of sugar for the production of ethanol via fermentation may negatively impact the use of farmland for production of food. Thus, alternative sources of fermentable sugars, particularly from lignocellulosic sources, have been extensively investigated. Another source of fermentable sugars with substantial potential for ethanol production is the waste from the food growing and processing industry. Reviewed here is the use of waste from potato processing, molasses from processing of sugar beets into sugar, whey from cheese production, byproducts of rice and coffee bean processing, and other food processing wastes as sugar sources for fermentation to ethanol. Specific topics discussed include the organisms used for fermentation, strategies, such as co-culturing and cell immobilization, used to improve the fermentation process, and the use of genetic engineering to improve the performance of ethanol producing fermenters.