RELATIONSHIPS BETWEEN FUNGAL GROWTH, MORPHOLOGY AND FUMARIC-ACID PRODUCTION BY RHIZOPUS-ARRHIZUS

Supplementation of a glucose-peptone medium with carboxymethyl cellulose (CMC) altered the morphology of shake flask cultures of Rhizopus arrhizus from clumped pellets to dispersed mycelia, and increased fumaric acid production from 1·78 gl−1 to 5·36 gl−1. However, supplementation of the medium with Carbopol resulted in a clumped-dispersed morphology, with significant reduction in fumaric acid production compared to the control. In fermenter cultures at pH 5·5 mycelium was uniformly distributed throughout the culture, but as aggregates of ca 1 cm diam with hyphae protruding, and high fumaric acid levels were observed. Supplementation of medium with CMC in fermenters promoted production of biomass at the expense of fumaric acid. The capacity to convert glucose to fumaric acid was greater in biomass produced in media supplemented with CMC. Low rates of fumaric acid production were observed in biotransformations when the mycelium was recovered from media containing Carbopol or when Carbopol was incorporated into the biotransformation medium. © 1990, British Mycological Society. All rights reserved.