Production of C4 and C5 branched-chain alcohols by engineered Escherichia. coli

Metabolic engineering of Escherichia coli for the production of isobutanol: a review

With the ongoing depletion of fossil fuel resources and emerging environmental issues, increasing research effort is being dedicated to producing biofuels from renewable substrates. With its advantages over ethanol in terms of energy density, octane number, and hygroscopicity, isobutanol is considered a potential alternative to traditional gasoline. However, as wild-type microorganisms cannot achieve the production of isobutanol with high titers and yields, rational genetic engineering has been employed to enhance its production. Herein, we review the latest developments in the metabolic engineering of Escherichia coli for the production of isobutanol, including those related to the utilization of diverse carbon sources, balancing the redox state, improving isobutanol tolerance, and application of synthetic biology circuits and tools.

Reducing higher alcohols by nitrogen compensation during fermentation of Chinese rice wine

Excessive amount of higher alcohols in alcoholic beverages causes unwell and side-effect for consumers although adequate consumption offers joy and pleasure. Therefore, reducing higher alcohols in alcoholic beverages is necessary. We used nitrogen compensation to reduce higher alcohols with Chinese rice wine as an experimental model. Higher alcohols including isobutyl alcohols, isoamyl alcohols, and β-phenethyl alcohols were significantly decreased by 19.27, 23.03 and 19.43%, respectively, when 200 mg/L (NH₄)₂HPO₄, 5% (w/v) yeast, and 11% wheat Koji were added to fermentation broth. Meanwhile, important quality parameters remained unchanged including free amino acids, organic acids, biogenic amines, and esters. The expression of glutamate dehydrogenase 1 gene (GDH1) and glutamine synthetase gene (GLN1) was significantly enhanced, 26.9- and 1.9-folds respectively. These results suggest that ammonium compensation could effectively decrease higher alcohols in Chinese rice wine by activating glutamate dehydrogenase (GDH) pathway in ammonium assimilation.