In recent years, carboxylic acids, such as lactobionic acid (LBA) have emerged as specialty acids due to their unique physiochemical properties. They are high value-added organic acids, with numerous applications that span the pharmaceutical, food, and cosmetics industries. Its sister chemical cellobionic acid is expected to have similar applications. In order to compete with petroleum-based processes for the production of carboxylic acids, the development of microbial processes utilizing low-cost substrates is essential. LBA is currently produced through chemical synthesis in an energy-intensive process requiring costly metal catalysts. Alternatively, LBA or CBA can be produced biologically by various bacterial and fungal strains using refined sugars as the substrate. Cellulosic biomass, which is available at low cost and in widespread abundance, is a potential alternative substrate for the bio-production of carboxylic acids. In this study, we report engineering Neurospora crassa strain for the production of cellobionic acid (CBA), directly from cellulose with exogenous laccase and redox mediator addition.
In this study, we report the production of cellobionic acid (cellobionate) directly from cellulosic biomass by a genetically engineered fungus strain Neurospora crassa. After deleting nine genes essential for cellobiose and cellobionate utilization and over-expressing laccase gene from Botrytis aclada, the engineered strain is able to convert pretreated poplar to cellobionate at high yield without addition of any exogenous enzymes.