Marziyeh Aghababaie - Biotechnology Department, New Science and Technology Faculty, University of Isfahan
Morteza Khanahmadi - Biotechnology Department, New Science and Technology Faculty, University of Isfahan
Masood Beheshti - Biotechnology Department, New Science and Technology Faculty, University of Isfahan
Maryam Mirlohi - Biotechnology Department, New Science and Technology Faculty, University of Isfahan

Industrial production of starter cultures is a note worth field of biotechnology which is strongly required in food industry especially in developing countries. Lactobacillus delbrueckii ssp bulgaricus is one of the yogurt starters. To determine the effect of temperature and pH for the production of a native strain of L. bulgaricus this study was designed using response surfacemethodology in 12 batch pH-controlled culture of lactobacillus delbrueckii subssp bulgaricus. Growth-associated and nongrowth-associated produce formation parameters a and b was estimated with Luedeking-Piret equation. Effect of pH and temperature on maximum biomass concentration (Xmax), maximum specific growth rate (μmax), Total lactic acid concentration (P), a and bparameters has been identified. Second order model for Xmax, μmax and P was significant but a and b was almost constant. Parameter a was about 0.6 g lactic acid.gbiomass-1 and parameter b was about 1 g lactic acid.gbiomass-1.h-1. Optimum temperature and pH for maximum biomass andspecific growth rate and acid production were 44°C and 5.7. This study provided the data requiredto develop a model for kinetic analysis of a native strain of L. bulgaricus growth and lactic acid production.

Response surface methodology; Lactobacillus bulgaricus, Whey, Lactic acid production