Rice straw to fuel ethanol standardisation of pre treatment enzymatic hydrolysis and fermentation strategies

Abstract

The present study is one of its kind, where one feedstock, rice straw, was utilized efficiently utilized for enzyme as well as ethanol production. For this, a fungal strain Aspergillus niger P-19 was selected from the already available fungal isolates present in the laboratory. Further, the optimization studies were carried out to improve the yields of all the enzyme components by using OVAT, PB, and RSM methods which resulted in improvement in the enzyme productivities. The previous reports that exist for the optimization of enzyme production using untreated rice straw have co-produced very few enzymes. Thus, the optimization study to co-produce such a broad consortium of cellulases and hemicellulases using untreated rice straw novelty to the study. The enzyme preparation was highly efficient in hydrolyzing alkali pretreated after 120 h of hydrolysis at 50°C releasing 78.34 mg/ml of reducing sugars and 48.45 mg/ml of glucose with 97.92% of carbohydrate conversion efficiency. On fermenting sugars with hexose and pentose fermenting yeasts, 25.74 g/l of alcohol was produced with fermentation efficiency of 77.22%. The study successfully validated a low-cost process involving solidstate fermentation of rice straw producing high titers of cellulases and hemicellulases for hydrolysis of alkali pretreated rice straw leading to ethanol production. newline