Screening of fungi capable of degrading lignocellulose from plantation forests

β-glucosidases from a new Aspergillus species can substitute commercial β-glucosidases for saccharification of lignocellulosic biomass

β-Glucosidase activity plays an essential role for efficient and complete hydrolysis of lignocellulosic biomass. Direct use of fungal fermentation broths can be cost saving relative to using commercial enzymes for production of biofuels and bioproducts. Through a fungal screening program for β-glucosidase activity, strain AP (CBS 127449, Aspergillus saccharolyticus ) showed 10 times greater β-glucosidase activity than the average of all other fungi screened, with Aspergillus niger showing second greatest activity. The potential of a fermentation broth of strain AP was compared with the commercial β-glucosidase-containing enzyme preparations Novozym 188 and Cellic CTec. The fermentation broth was found to be a valid substitute for Novozym 188 in cellobiose hydrolysis. The Michaelis-Menten kinetics affinity constant as well as performance in cellobiose hydrolysis with regard to product inhibition were found to be the same for Novozym 188 and the broth of strain AP. Compared with Novozym 188, the fermentation broth had higher specific activity (11.3 U/mg total protein compared with 7.5 U/mg total protein) and also increased thermostability, identified by the thermal activity number of 66.8 vs. 63.4 °C for Novozym 188. The significant thermostability of strain AP β-glucosidases was further confirmed when compared with Cellic CTec. The β-glucosidases of strain AP were able to degrade cellodextrins with an exo-acting approach and could hydrolyse pretreated bagasse to monomeric sugars when combined with Celluclast 1.5L. The fungus therefore showed great potential as an onsite producer for β-glucosidase activity.

Decomposition of lignin and holocellulose on Acacia mangium leaves and twigs by six fungal isolates from nature

This research was conducted in the aim of preventing wild fire through reducing potential energy source to become in situ fertilizer. To prevent forest fires by reducing wood waste using lignocellulose-degrading fungi, six fungal isolates were tested for lignin and cellulose-degrading activity with Acacia mangium leaves and twigs over a period of 1 to 3 months. The fungi degraded 8.9-27.1% of the lignin and 14-31% of the holocellulose. The degradation rate varied depending on the fungal species. An increase in incubation time tended to decrease the amounts of holocellulose and lignin. However, the hot water soluble tended to increase following a longer incubation period. From the results obtained here, more time was needed to degrade lignin rather than other components in the sample.