Saccharification with Phanerochaete chrysosporium and Pleurotus ostreatus enzymatic extracts of pretreated banana waste

Abstract

Lignocellulosic biomass has a great potential as raw material for second and third generation biofuels since it is the most abundant carbohydrate on earth and the main component of agricultural waste; however, saccharification of lignocellulosic biomass is crucial for the establishment of a carbohydratebased economy. The use of fungal enzymes is the preferred procedure for lignocellulosic saccharification. Fungi such as basidiomycetes (e.g Phanerochaete chrysosporium) produce cellulolytic/hemicellulolytic and ligninolytic enzymes, which are responsible for lignocellulose degradation. In this study the saccharification of banana flour prepared from pseudostem and green non commercial-grade fruit (1:1), two of the main agro-waste of banana industry was investigated. The material was pretreated by physical and chemical processes including drying and grinding, followed by 3% HCl or 3% NaOH hydrolysis, or a sequential pretreatment with 3% HCl first and then 3% NaOH and heated at 121°C, at 15 Lb/in² for 15 min. The highest concentration of reducing sugars (RS) was obtained with acid hydrolysis (42.41 gL^-1). Crude cellulolytic-ligninolytic enzymatic extracts from Pleurotus ostreatus and P. chrysosporium cultured on banana waste as the only carbon source were prepared and used for the saccharification. Surprisingly, P. chrysosporium crude extract produced a decrease in RS (2.27 gL^-1). Although P. ostreatus cellulose activity (17,777.78 UL^-1) was almost half compared to P. chrysosporium’s (31,296.30 UL^-1), the former produced an increment in the release of RS (63.65 gL^-1). In Mexico, banana is one of the main crops and generates large agricultural waste after harvest. According to the results obtained with acid-heat pretreatment followed by saccharification with P. ostreatus enzymatic crude extract, banana agro-waste can be considered as a potential feedstock for RS-based bioproducts like bioethanol.

Key words: Banana waste, lignocellulosic, pretreatments, saccharification, reducing sugars.