title: Pretreatment of fibrous biomass and growth of biosurfactant-producing Bacillus subtilis on biomass-derived fermentable sugars.
abstract: Pretreatment of six fibrous biomasses (switchgrass, alfalfa, soy hulls, soy fiber, DDGS and Baggase) and subsequent hydrolysis using cellulolytic enzymes at a 2.5% (v/v) and 5% (v/v) loading 2.5 (v/v) and 5% (v/v) loading was compared for higher amounts of sugars released. Soaking of biomasses of switchgrass, alfalfa, soy hulls and bagasse in 15% w/w ammonia was optimal at 60 °C for 12 h, followed by enzymatic hydrolysis, yielding 72, 70, 80 and 75% carbohydrate conversions, respectively. However, soaking in ammonia was not needed for soy fiber and DDGS as these contained very little lignin. Ultrasonication for 3 min @ 100% amplitude (170 µM) was found to be optimal for soy fiber and DDGS from which 77 and 83% carbohydrate conversion, respectively, was obtained following enzyme treatment at 5% (w/v) enzyme. The sugars released by enzymatic hydrolysis of pretreated biomass were utilized as an energy source by Bacillus subtilis in fermentation media at 2% (w/v) of concentration. In shake flask trials, cell growth was 15-20% higher on hydrolysates of ammonia-treated switchgrass and alfalfa vs. glucose-based control media due to the presence of a wider range of monomeric sugars (glucose, xylose, arabinose, mannose and galactose). In contrast, growth was less on soy hull hydrolysates prepared with ammonia pretreatment.
authors.affiliation: Department of Food Science and Human Nutrition, Iowa State University, 2312 Food Science Building, Ames, IA, 50011, USA.
authors.forename: Rajat
authors.initials: R
authors.lastname: Sharma
authors.affiliation: Department of Food Science and Human Nutrition, Iowa State University, 2312 Food Science Building, Ames, IA, 50011, USA. lamsal@iastate.edu.
authors.forename: Buddhi P
authors.initials: BP
authors.lastname: Lamsal
authors.affiliation: Center for Crop Utilization Research, Iowa State University, Ames, IA, 50011, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Colonna
mesh_terms: D001412:Bacillus subtilis / Q000737:chemistry / Q000254:growth & development*; D018533:Biomass; D009005:Monosaccharides / Q000096:biosynthesis* / Q000737:chemistry; D013501:Surface-Active Agents / Q000378:metabolism*
chemical_list: D009005:Monosaccharides; D013501:Surface-Active Agents
keywords: Bacillus subtilis; Biomass pretreatment; Biosurfactants; Enzymatic hydrolysis; Liquid ammonia; Ultrasonication