Biological pretreatment of rice straw using an alkalophilic fungus MVI.2011 for enhanced enzymatic hydrolysis yield

Abstract

Ethanol from agricultural residues is a sustainable energy source, but involves complex steps like pretreatment for the removal of lignin. Conventional pretreatment methods make use of costly chemicals or energy intensive machines. Alternatively, biological pretreatment methods are sustainable, energy and cost efficient, but take at least two weeks to bring about delignification. An alkalophilic dimorphic dueteromycete coded MVI.2011, has been known to synthesize large quantities of ligninases in a short span of time; ligninases being the key enzymes in the biological delignification of lignocelluloses. Therefore, in this study, the effectiveness of this fungus in the delignification of rice straw is explored, with a view to reduce the pretreatment time. Solid state cultivation of rice straw with MVI.2011 for two weeks and submerged cultivation for one week showed 54% and 74.2% improvement in percentage of saccharification after enzymatic hydrolysis. The results of fungal pretreatment in 7.5 l bioreactor are also promising and faster than existing biological methods. Percentage of saccharification can be improved further, if submerged cultivation conditions are optimized to minimize the cellulolytic and hemicellulolytic activities of the fungus. Hence pretreatment with MVI.2011 is a potential alternative to the prevailing time-consuming fungal pretreatment methods for sustainable ethanol production.