ABSTRACT
Microbial exopolysaccharides (EPS) are considered as natural bio-thickeners abundantly used in dairy and fermented food industries for quality improvement. In fermentation based dairy industries, researchers are seeking their attention on substitution of artificial food stabilizers with naturals by exploring EPS, especially for improving the rheology of fermented food products. Lactic acid bacteria (LAB) being a starter player for fermented food products are believed to be as one of the best natural producers of EPS. These EPS are basically sugar residues, secreted by microbes in their surrounding environment but their in-vitro production is not economical due to the media and processing costs involved. The process of production is also complex due to the involvement of various enzymes and regulatory proteins. With modernization in dairy sector, our understanding towards EPS needs improvement. The review focuses on a brief explanation on the behavior and functionality of EPS from lactic acid bacteria.
ABSTRACT
Aims: Selective enumeration, isolation and characterization of lactic acid bacteria from different raw milk sources with special elucidation to lactic acid production. Study Design: Serial dilution for strain isolation from raw milk samples to be done followed by complete morphological, biochemical and molecular characterization aiming to study the microbial behavior to ferment different sugar and producing lactic acid as end product. Place and Duration of Study: Microbiology Biotechnology Laboratory, Tropilite Foods Pvt. Ltd. Gwalior (M.P)-INDIA from Sep 2012 to April 2013. Methodology: Milk samples from cow, sheep, goat, camel and buffalo were collected from the surrounding area of Gwalior district of Madhya Pradesh, India, from local milk suppliers. 13 potent strains in terms of lactic acid production were selected for analysis. Gram Staining, Catalase activity, Sugar fermentation, growth at high (45ºC) and low (10ºC) temperatures along with growth in different NaCl concentrations was observed with all isolates. Significant molecular characterization was done to determine the homology between different isolates of lactic acid bacteria. Results and Conclusion: Five potent lactic acid bacteria strains Streptococcus thermophilus from goat milk, Lactococcus lactis from buffalo milk, Streptococcus gallolyticus from camel milk, Streptococcus thermophilus from cow milk, Lactobacillus delbrueckii from sheep milk were identified capable of producing lactic acid in generous amount. Also all isolated strains from goat milk were found efficient in terms of lactic acid production when compared to other raw milk sources.