Volume No. 7 Issue No.: 1A Page No.: 234-244 July-September 2012




Choksi Nikita and Desai Hemangi*

TIFAC-CORE In Environmental Engineering, Sarvajanik College of Engineering and Technology Surat, Gujarat (INDIA)


Received on : May 02, 2012




Lactic Acid Bacteria (LAB) commonly used as starter cultures in food technology are known to manufacture antimicrobial products having great potential. The aim of this study is isolation of lactic acid bacterial strain which has been potential for lactic acid production, to identify, characterize it and to optimize culture conditions for the process. For this study, we have isolated different strains of Lactic Acid Bacteria (LAB) from dairy sludge samples which were collected from 3 different dairy plant of Gujarat, (India). Therefore, characterization of isolated strains through morphological, physiological, biochemical and carbohydrate fermentation test were done. Lactic Acid Bacteria (LAB) are a group of Gram–positive, non–spore forming, cocci or rod shaped, catalase–negative and fastidious organisms, considered as ‘Generally Recognized As Safe’ (GRAS) organism. For isolation, samples were serially diluted and plated on MRS agar (DE MAN, ROGOSA and SHARPE agar. HI Media) Plate. Well–isolated colonies with typical characteristics were picked from each plate and were further sub cultured until pure isolates were obtained and transferred to MRS broth (HI Media) for further experiments. Identification of lactic acid bacteria belongs to family Lactobacillaceae was done first at genus level in the Lactobacillus, Lactococcus, Streptococcus, Leuconostoc, Pediococcus. Lactobacillus is rod shape and Streptococcus, Leuconostoc, Pediococcus are cocci shape. Most of them are used in dairy starter culture, present in raw milk, milk–loving bacteria. Isolated colony was identified by gram–staining, gram +ve and rod shape strain showed confirmation of lactobacillus . L.bulgaricus and Streptococcus thermophilus were found as the most dominant species in common sludge unit. While L.acidophillus was found as dominant species along with the L.bulgaricus and Streptococcus thermophilus in the sludge of pro biotic acidophilus butter milk manufacturing unit and L.casei, L.helveticus, L.brevis, L.lactis were present as the dominant species in the cheese manufacturing unit along with the L.bulgaricus and Streptococcus thermophilus. Selected microbial isolates obtained in this study will be used for production of lactic acid acts as monomer for the synthesis of biodegradable polymer on my future study.


Keywords : Lactic Acid Bacteria (LAB), Isolation, Dairy sludge, MRS agar plate,