Combined effects of high hydrostatic pressure and specific fungal cellulase improve coconut husk hydrolysis

Abstract

Cellulosic ethanol production may serve in the development of a viable renewable fuel. An important contribution to bio-economy and sustainability could be achieved by using coconut husks, thousands of tons of which are discarded every day in tropical regions. However, high production costs have hindered this application of a common refuse. In this work, we propose a process to improve coconut husk hydrolysis for ethanol production. To achieve this improvement, we applied a combined method. First, a treatment based on high hydrostatic pressure (HHP) increased the hydrolytic performance of cellulases on recalcitrant coconut husk. Second, isolated cellulase from the submerged fermentations of coconut-specific fungi were used for coconut husk hydrolysis under pressure. Interestingly, specific cellulases produced by these fungi outperform the industry standards in the hydrolysis of coconut husk under pressurised conditions. Additionally, HHP improves cellobiase activity, which reduces the cellobiose-dependent inhibition of biomass hydrolysis. An increase in coconut husk hydrolysis by a factor of 2 was achieved as a result of the combined effects of HHP treatment and the action of specific fungal cellulases. In this work, we propose the use of a new fungus, Penicillium variabile, as a source of cellulase in combination with HHP as a novel process for coconut hydrolysis.