Background: Sclerotium rolfsii is a potent producer of many secondary metabolites, one of which like scleroglucan is an exopolysaccharide (EPS) appreciated as a multipurpose compound applicable in many industrial fields. Results: Aspartate transaminase (AAT1) catalyzes the interconversion of aspartate and α-ketoglutarate to glutamate and oxaloacetate. We selected AAT1 in the oxalate metabolic pathway as a target of CRISPR/Cas9. Disruption of AAT1 leads to the accumulation of oxalate, rather than its conversion to α-ketoglutarate (AKG). Therefore, AAT1-mutant serves to lower the pH (pH 3–4) so as to increase the production of the pH-sensitive metabolite scleroglucan to 21.03 g L⁻¹ with a productivity of up to 0.25 g L⁻¹·h⁻¹. Conclusions: We established a platform for gene editing that could rapidly generate and select mutants to provide a new beneficial strain of S. rolfsii as a scleroglucan hyper-producer, which is expected to reduce the cost of controlling the optimum pH condition in the fermentation industry.

This work demonstrates asymmetric synthesis of the GABA derivative ( R )-baclofen and a new herbicidal mode-of-action inhibitor (3 S ,4 S )-tetflupyrolimet featuring low loading (0.5 mol%) organocatalytic addition reactions of dithiomalonates to nitrostyrenes under “on water” conditions.

Facile access to 4-aryl-6-oxycarbonyl-2-pyrones from α-halothioesters with β,γ-unsaturated α-keto esters is achieved via a DBU-promoted Michael addition/lactonization/elimination cascade reaction. The reaction mechanism is tentatively elucidated by performing control experiments and high-resolution mass spectrometry analysis, which indicates that the cascade sequence may involve DBU-derived ammonium ylides.