Evaluation of a Minimal Energy-Dependent Technique for Preparation of Ailanthus excelsa Hemicellulose Acid Hydrolysate Fermentable by Schefferomyces stipitis

Abstract

A low-energy-dependent sustainable technique for the preparation of hemicellulose hydrolysate from the wood chip of low input and less care-demanding tree, Ailanthus excelsa Roxb., involving two-stage dilute acid hydrolysis technique followed by fermentation by pentose (PS)-fermenting yeast, Schefferomyces stipitis (NCIM 3507), was standardised. The main parameters optimised were acid concentration and heating period. The maximum sugar yield was obtained by hydrolysis with 10% (v/v) sulphuric acid applying pressure at 120°C for 4 min. The hydrolysate thus obtained and treated (treated hemicellulose acid pre-hydrolysate (THAP) with lime and sodium sulphite, however, could not be fermented with S. stipitis, indicating the presence of inhibitors in intolerable concentration. Though it contained lesser sugars, the hydrolysate obtained with 1% acid and treated as above (THAP) could be easily fermented by yeast. Ethanol yield as a result of fermentation of hydrolysate medium containing 40, 50 and 70% of THAP was 8.47, 6.28 and 5.09 g/l, respectively, after 120 h. This paper highlights the use of woody material, A. excelsa, a fast-growing tree adapted for marginal land, as a source of hemicellulose acid hydrolysate fermentable by S. stipitis by applying modified two-stage dilute acid hydrolysis technique with minimal energy input.