A novel membrane-surface liquid co-culture to improve the production of laccase from Ganoderma lucidum

• A potential laccase producer was separated and identified.
• A novel biomembrane-surface liquid co-culture was developed to improve laccase production.
• Glucose limitation in fermentation broth induces the secretion of laccase.
• Metabolites produced by Saccharomyces cerevisiae are the key reason for improvement of laccase activity.
• Laccase production by BSLCc was successfully scaled-up to 100 l reactor.

In this work, a laccase producer, Ganoderma lucidum, was separated and identified according to its morphological characteristics and phylogenetic data. A 4000 U/l and 8500 U/l of laccase activity was obtained in 500 ml flask by submerged culture and biomembrane-surface liquid culture (BSLC), respectively. Furthermore, the novel biomembrane-surface liquid co-culture (BSLCc) was developed by adding Saccharomyces cerevisiae to reactor in order to shorten the fermentation period and improve laccase production. Laccase activity obtained by BSLCc, 23 000 U/l, is 5.8 and 2.7 times of that obtained by submerged culture and BSLC, respectively. In addition, laccase production by BSLCc was successfully scaled-up to 100 l reactor, and 38 000 U/l of laccase activity was obtained on day 8. The mechanism of overproducing laccase by BSLCc was investigated by metabolism pathway analysis of glucose. The results show glucose limitation in fermentation broth induces the secretion of laccase. The addition of S. cerevisiae, on one hand, leads to an earlier occurrence of glucose limitation state, and thus shortens the fermentation time; on the other hand, it also results in the appearance of a series of metabolites of the yeast including organic acids, ethanol, glycerol and so forth in fermentation broth, and both polyacrylamide gel electrophoresis analysis and enzyme activity detection of laccase show that these metabolites contribute to the improvement of laccase activity.