Tuesday, April 20, 2010
8-37

Optimization of microwave assisted lime pretreatment of sweet sorghum bagasse for enzymatic saccharification

Ruplal Choudhary1, A.H.L. Umagiliyage1, Y. Liang2, and J. Haddock3. (1) Plant, Soil and Agricultural Systems, Southern Illinois University, 1205 Lincoln Drive Room 176, Carbondale, IL 62901, (2) Civil and Environmental Engineering, Southern Illinois University, 1205 Lincoln Drive Room 176, Carbondale, IL 62901, (3) Microbiology, Southern Illinois University, 1205 Lincoln Drive Room 176, Carbondale, IL 62901

Lignocellulosic feedstocks are the major sources of carbohydrate polymers that have high potential for biochemical conversion to fermentable sugars. Sweet Sorghum is a high efficiency crop that yields higher biomass with lower inputs. It produces sugars that can be pressed to express juice for direct fermentation to ethanol. The pressed stalk (bagasse) is rich in structural carbohydrates and has potential to yield 400 gallons of cellulosic ethanol per acre of sweet sorghum crop.

Our research objective is to optimize microwave assisted lime pretreatment of sweet sorghum bagasse for its enzymatic conversion to fermentable sugars. Sweet sorghum biomass was ground and passed through a 40 mesh screen. Moisture content of the biomass was approximately 12%. It had 48% cellulose, 21% hemicelluloses, and 15% acid detergent lignin on dry matter basis. Lime pretreatment was provided in a microwave oven at 1 atmospheric pressure. The lime concentration was 0.05, 0.10 and 0.15 g/g biomass; reaction time in a microwave oven was 10 min, 20 min and 30 min. Liquid loading was varied from 10 to 20 ml water /g biomass sample. Pretreated biomass was hydrolyzed with a commercial enzyme AcceleraseTM 1000, and tested for total reducing sugars and lignin content.  A linear trend was observed showing a steady increase in sugar yield and lignin degradation with increased dose of lime and increasing time of microwave treatment. The preliminary data has shown a high potential for lime pretreatment as a cheaper process for production of fermentable sugars from sweet sorghum bagasse.


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