A Strategy for Scleroglucan Production in Sclerotium Rolfsii: Lowering pH in Fermentation Process by Manipulating Oxalate Metabolic Pathway With CRISPR/Cas9 Tool

Abstract

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: We chose AAT1 gene in oxalate metabolic pathway as target of CRISPR/Cas9. When the AAT1 gene is disrupted, oxalate was not converted to α-ketoglutarate (AKG), but accumulated. So AAT1-mutant serves to lower the pH (pH 3-4) to increase the production of the pH-sensitive metabolite scleroglucan to be 21.03 g l-1 with productivity reached 0.25 g/(L·h).Conclusions: We established a platform for gene editing to rapidly generate and select mutants, and provide a new beneficial strain of S. rolfsii as a scleroglucan hyper-producer which could also reduce the cost of controlling optimum pH condition in fermentation industry.