| Summary: | 碩士 === 國立屏東科技大學 === 食品科學系 === 92 === Breeding of Lactobacillus bulgaricus was performed by protoplast fusion to enhance its starch utilization ability. Protoplast of L. bulgaricus was prepared by lysozyme and fused with the chloroplast of Brassica alboglabra Bail. The protoplast and chloroplast were fused in the presence of CaCl2 and polyethyleneglycol (PEG) 4000. The Fused cells were grown on a regeneration medium and then the acid producing fusant was selected. Furthermore, physiological characteristics of the fusant were also evaluated. The results showed that, the fusant did not only utilize starch, but also utilized the other carbon sources such as dulcitol, melezitose, raffinose, rhamnose, a-methyl-D-glucoside, sucrose, salicin, sorbitol, trehalose, ribitol, mannitol and xylitol. Besides that, the fusant also could utilize (NH4) 2HPO4 and casamino acid, which found to be superior to its parental strain. The soy bean milk (no sugar) containing 1%glucose, 1%potato starch, and 1% of skimmed milk incubated at 16h resulted in production of acid at different levels as followed: 0.56%, 0.79%, 0.77% and 0.9%, respectively. In addition, the fusant increased the assimilation ability of hydrocarbon compounds, such as cyclopentane, n-dodecarbon, n-heptane, n-hexadecane, n-haxadecane, isopentane, kerosene, n-decane, n-nonane, n-octane, n-undecane, iso-octanen, n-tetradence. Optimum culture conditions for fusant growth were following: 3%potato starch, 4%yeast extract, pH 6.5, at temperature of 37℃ and 100 rpm. Optimum culture conditions for high acid-producing fusant were following: 3%potato starch, 4%yeast extract, pH 8.0, and incubated at a static temperature of 37℃. The extracellular enzyme produced from this fusant had ability to degrade starch. The result showed that the increasing of preculture time of fusant provided a higher starch hydrolysis activity which than Bacillus subtilis high.
key word:Lactobacillus bulgaricus, protoplast, fusion, fusant.
|
|---|
