99A-34 |
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C. RUENGRUGLIKIT and Y. D. Hang. Food Science & Technology, Cornell Univ., New York State Agricultural Experiment Station, 630 W. North St., Geneva, NY 14456-1371 Production of polylactic acid (PLA) requires optically pure lactic acid. Lactic acid production by carbohydrate fermentation can produce a desired stereoisomer, unlike the chemical process. Lactobacillus delbrueckii ATCC 4797 is a homofermentative lactic acid bacterium producing mainly D-lactic acid. The fermentation production of lactic acid must be cost-competitive with chemical synthesis. Media can comprise up to 30% of the cost of fermentation. Corn cobs can be used as a cheap medium for microbial fermentation. The objective of this work was to study the possibility of using corn cobs as a low-cost medium for the production of D-lactic acid by Lactobacillus delbrueckii ATCC 4797. Corn cobs (50, 100, 200 g/L) were pretreated with 0.1 N NaOH and then acidified to desired pH (3.5, 4.5, 5.5) and autoclaved. Simultaneous saccharification and fermentation (SSF) was conducted in 2.0 L BioFlo fermenter with a working volume of 1.0 L at 450C and 100 rpm. 1% (v/v) each of a commercial juice processing enzyme, Rapidase Pomaliq and inoculum were added to the medium. 1.0 N NaOH was used to neutralize the lactic acid by pH controller to keep pH constant at desired pH. D-lactic acid and sugars (cellobiose, glucose, xylose, arabinose) were determined by HPLC using a Bio-Rad HPX-87H column (300 x 7.8 mm) with RI detector. The concentrations of corn cobs and pH were found to have a significant effect on the production of D-lactic acid by Lactobacillus delbrueckii ATCC 4797. Under optimal conditions (50 g/L corn cobs, and pH 5.5), Lactobacillus delbrueckii ATCC 4797 yielded 533 g of D-lactic acid per kg of dry matter of corn cobs after 96 hr of fermentation at 450C. The results of this study indicate that corn cobs can serve as a renewable source of biomass for production of D-lactic acid by Lactobacillus delbrueckii ATCC 4797.
Session 99A, Biotechnology: General
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