Abstract

The effect of physical (subcritical water) and chemical (acid and alkali) pretreatment on conversion of lignocellulose (cellulose, hemicellulose) in water hyacinth (WH) was investigated. The highest sugar content in acid pretreated samples was observed in WH treated with 3% H₂SO₄ solution (up to 18.16% w/w). Alkali treatment had nearly no effect on conversion of lignocellulose in WH to sugar. Combinations of acid or alkali pretreatments with enzyme treatment resulted in drastic increase of sugar in samples (up to 31.2 and 22.9 % w/w, respectively). In addition, increasing the applied enzyme concentration from 0.8% w/w (on dry WH basis) to 4% further increased the sugar content in the sample (up to 50.5% w/w). Subcritical water (SCW) (200°C and 10 min) and subsequent enzyme treatment resulted up to 17% w/w sugar in samples.Bioethanol concentration during fermentation (at 30°C) of pretreated sample usingSaccharomyses cerevisae increased with increasing the fermentation time. After 3 days fermentation, up to 60% of sugar in the sample was converted in ethanol.

Key words: Bioethanol, subcritical water, chemical methods, water hyacinth.