USE KILLER TOXIN EXTRACTED FROM BAKERY YEAST FOR EXTENDING SHELF LIFE OF FRUITS

Abstract

Dry Bakery yeast was used to production of killer toxin. Purification steps included use of (NH4)2SO4 30-70% saturated solution and Sephacryl S-200, giving two peaks that collected to give inhibition zones of 28 and 22mm diameter for Escherichia coli and Salmonella typhimurium respectively, with 10.6% yield from the total protein 13.7mg\ml of yeast crude extract. The effect of killer toxin and pullulan coating on growth of some selected microorganism's strains showed inhibition of growth of E. coli, S. typhimurium, Aspergillus ssp., Penicillium ssp., Candida albicans and Pichia jadinii a was 71, 62, 52, 59, 68 and 76% respectively, at a rate of 64.6% for killer toxin (K), and was 68, 70, 42, 48, 61 and 63% respectively, at a rate of 58.6% for pullulan (P), and 74, 68, 65, 68, 71 and 73% respectively, at a rate of 69.83% for 25% P+75% K, and was 83, 76, 72, 81, 76 and 87% respectively, at a rate of 79.16% for 50% P+50% K, and was 67, 72, 54, 56, 64 and 69% respectively, at a rate of 63.66% for 75% P+25% K. The percentage values of weight loss for uncoated and coated apples with 100% (K), 100% (P), 50% K+50% P, 25% K+75% P and 75% K+25% P solutions were 3.2, 4.8, 6.1, 7, 7.2, 8.3 and 9.1%; 3.3, 4.2, 5.1, 5.6, 6.1, 7.2 and 8.3%; 2.9, 3.8, 4.1, 4.6, 5.8, 6.4 and 7.6%; 2.6, 2.8, 3.2, 3.3, 4, 4.7 and 5.1%; 2.9, 3.3, 3.5, 4.1, 5.3, 5.7 and 6%; 3, 3.5, 3.7, 4.4, 5.6, 5.9 and 6.5% respectively, when storage at 25°C for 3, 6, 9, 12, 15, 18 and 21 day respectively, while observe spoilage time (days) during apples storage at 25°C showed that the spoilage began to appear at 4, 14, 7, 19, 9 and 12 day for uncoated and coated apples with 100% (K), 100% (P), 50% P+50% K, 25% K+75% P and 75% K+25% P respectively