Strategies for Fermentable Sugar Production by Using Pressurized Acid Hydrolysis for Rice Husks

This study investigated the use of leftover biomass (rice husks) as the raw material for the biotechnological production of platform chemicals and biopolymers. Following the biorefinery concept, different acid hydrolysates were studied and resulted into a wide range of treatment strategies. Chemometrics were applied throughout the procedures in multivariate experimental conditions. By using the best hydrolytic conditions of 6.0% H3PO4, 135°C (45MPa) and reaction time of 62min, 21.0g/L sugar hydrolysates were produced; by using the best hydrolytic condition of 4.5% HNO3, 135°C/35min, 16.1g/L sugar hydrolysates were produced; and with the hydrolysates use of 1.5% H2SO4 and 1.5% HCl, 135°C/62min, 18.2 and 17.8g/L sugar hydrolysates were produced, respectively. The highest productivity, in terms of fermentable sugars, reached 68% of integral cellulose/hemicellulose fraction and surpassed those found in the literature, with regard to the processing of rice husks, by considering just one step process. Sulfuric hydrolysate, detoxified with active carbon, was used to prove this proposal viability, resulting in a fermentation substrate for A. terreus (ATCC10020) and R. radiobacter (LMG196) strains (natural producers of bioproducts), which certified the feasibility of the proposal. The production of fermentable sugars from leftover biomass should encourage a search for new bioconversion routes, which can result in economic and environmental benefits and a spread of knowledge.