Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Botany - Microbiology

Whey permeate disposal represents a serious environmental pollutant by increasing the biological oxygen demand in the water current due to its lactose content (about 50 gl-1). The present work adapted a microbial fermentation process to utilize the lactose content of whey in production of optically pure lactic acid which is widely involved in many industrial products as petrochemical- based polymers. Lactobacillus plantarum EMCC1039 and Lactobacillus dulbrueckii subsp. bulgaricus Lb-12 had been used in both free and immobilized cell states where yeast extract and casein hydrolysate (0.5%, 1% and 2% wv-1) in addition to corn and soy bean extracts (10% wv-1) were investigated separately as nitrogen sources. Fermentation experiments were carried out in static flasks in presence and absence of mineral salts; MgSO4.7H2O and 5 gl-1 of MnSO4.H2O at the ratio of 0.2% and 0.05% wv-1respectively. Yeast extract showed high lactic acid production (15 gl-1) and high lactose consumption (84%) by the immobilized Lactobacillus plantarum, while immobilized Lactobacillus bulgaricus on casein hydrolysate produced 14.88 gl-1 lactic acid and utilized 78% lactose. Corn / yeast extracts mixture was studied in different ratios with studying initial lactose concentration to adjust C/N Ratio for fermentation medium using chitosan-coated calcium alginate immobilized Lactobacillus bulgaricus. At 20% wv-1: 0.5% wv-1 ratio of corn extract: yeast extract, produced lactic acid was 26 g l-1 while the consumed lactose percent was 88%. By adaptation of the environmental conditions of the fermentation process at pH; 5.5, incubating temperature; 37, and inoculum volume at 2% wv-1 with shaking speed; 80 rpm, the batch microbial fermentation process produced 44 gl-1 lactic acid, lactic acid yield was 0.88 gg-1 while lactose was completely consumed in only 52 h. the present work saved the fermentation time and consumed energy of fermentation by about 27.7% and reduced the production cost by about 79%

Issued also as CD