Isolation, characterization and application of indigenous lactic acid bacteria in milk fermentation
By: Farah Nawaz, Sadia Mehmood, Shakira Ghazanfar S.S. Tahir, Naseem Rauf, Muhammad Imran
Key Words: Indigenous starters, Milk, Lactic acid bacteria, Nutrition.
Int. J. Biosci. 9(6), 415-430, December 2016.
Lactic acid bacteria are essential part of milk fermentation impart characteristic attributes on product physio- chemistry, nutrition and sensory properties. The present study was designed to characterize the Lactic acid bacteria isolated from fermented milk product Dahi for potential application in milk fermentation. All isolates were Gram positive rods and cocci. Most of the isolates were heterofermentative shown carbon dioxide production. Isolates shown higher lipolytic, proteolytic and fair amylolytic activity. Physiological characterization revealed that cocci were showing optimum growth at 2 and 4% NaCl while rods at 6.5% followed by 4% salt. Agglomerative hierarchical clustering (AHC) was done based on growth rate and alteration in media pH at differenttemperatures. Identification of representative isolates from each group was confirmed by 16SrRNA gene partial sequencing.Selective strains were identified as Lactobacillus delbrueckii QAULb01(KT021869), Streptococcus thermophilusQauSt1(KT021870)andLactobacillus delbrueckii Qaulbd16, and Enterococcus mundtii QAUEM02. Comparative fermentation experiments of commercial starter culture and indigenous isolates combination (QauSt1+Qaulb01) was done. The local strain combination shown more aroma as compare to commercial starter that was also confirmed by change in FTIR spectrum. Comparative physiochemical analysis shown that local cultures in term less syneresis, high solid content, stability in pH and acidity and higher viscosity.The nutrition of fermented milk produced by local strain in term mineral contents was comparable with significantly higher zinc and iron contents (K :720 mg/kg ), Na: 642.5 mg/kg, Ca: 245.2 mg/kg, Fe: 2.7 mg/kg and 2 mg/kg of Zinc). Hence these strains can be successfully used to replace starter cultures at commercial scale for fermented milks.