Biohydrogen production from pure and natural lignocellulosic feedstock with chemical pretreatment and bacterial hydrolysis

Abstract

Pretreatment and saccharification of lignocellulosic materials is the key technology affecting the efficiency of cellulosic biohydrogen production. In this work, two pure cellulosic materials (i.e., carboxymethyl-cellulose (CMC) and xylan) were directly hydrolyzed (without pretreatment) by a cellulolytic isolate Cellulomonas uda E3-01 able to release extracellular cellulolytic enzymes. Natural cellulosic feedstock (i.e., sugarcane bagasse) was chemically pretreated prior to the bacterial hydrolysis.A temperature-shift strategy (35 °C for cellulolytic enzymes production and 45 °C for hydrolysis reaction) was used to increase the production of reducing sugars during the bacterial hydrolysis. The hydrolysates of CMC, xylan, and bagasse were efficiently converted to H 2 via dark fermentation with Clostridium butyricum CGS5. The maximum hydrogen yield was 8.80 mmol H 2/g reducing sugar (i.e., 1.58 mol H 2/mol hexose) for CMC, 6.03 mmol H 2/g reducing sugar (i.e., 0.91 mol H 2/mol pentose) for xylan, and 6.01 mmol H 2/g reducing sugar for bagasse.