Optimisation of β-glucuronidase production from a newly isolated Ganoderma applanatum

Media optimisation was attempted for beta-glucuronidase production from a newly and locally isolated (Oxfordshire, UK) fungal strain of Ganoderma applanatum. Both fungal growth and beta-glucuronidase activity were found to be greatly affected by varying the carbon or the nitrogen source with gum arabic and yeast extracts being the best carbon and nitrogen sources, respectively. Their concentrations were optimised at 8 g L-1 for the former and 2 g L-1 for the latter. Work then proceeded to enhance the yield of beta-glucuronidase in a controlled environment. Control, batch and fed-batch cultivations were performed in 2-L bioreactors using the optimised medium supplemented with cellobiuronic acid as inducer. Time profiles of biomass dry weight, carbohydrate consumption and beta-glucuronidase production were obtained and the results showed that production of beta-glucuronidase was noticeably increased by the addition of cellobiuronic acid in both batch and fed-batch fermentations. Although the addition did not produce a variation in the pattern of growth seen between control, and induced fermenters, higher levels of the enzyme were attained when adopting a fed-batch process with 1.09 U mL(-1) of culture, corresponding to a 5-fold enhancement in beta-glucuronidase production rate compared with batch fermentation. (c) 2007 Elsevier B.V. All rights reserved.