SCREENING AND SELECTION OF MEDIA COMPONENTS FOR LACTIC-ACID PRODUCTION USING PLACKETT-BURMAN DESIGN

Plackett-Burman design was used to efficiently select important media components influencing lactic acid production in a two step screening procedure. A total of 36 screening experiments were conducted for stud ying the effect of various media components such as carbon and nitroge n (simple and complex) sources, minerals/buffering agents and a specif ic inducer for the production of lactic acid by Lactobacillus plantaru m NCIM 2084. The eleven ingredients chosen after the first screening e xperiments were further screened by a Plackett-Burman design consistin g of 12 experiments. Liquefied starch, wheat bran extract, ammonium ni trate, manganese sulphate and sodium acetate were chosen as promising ingredients for further optimisation studies. The highest yield of 41. 9 g/l of lactic acid was obtained at the end of 24 hours of fermentati on which corresponded to 90% conversion, on the basis of sugar supplie d.