碱性氨基酸修饰乳清蛋白基质凝胶功能性

将L-精氨酸(L-Arg)、L-赖氨酸(L-Lys)和L-组氨酸(L-His)分别加入到质量浓度为120 g/L的乳清蛋白溶液中,使每种氨基酸的最终质量浓度均分别为1、3和5 g/L,均质后再经90℃加热30 min制备热诱导凝胶,并探讨碱性氨基酸对凝胶功能的改造。通过物化、全质构、吸水性和凝胶电泳等分析手段,表征溶液的pH及其所成凝胶的形貌、质构、水化性质及凝胶内的蛋白浸出组分。结果表明,L-Arg、L-Lys及L-His均能明显提高蛋白成胶溶液的pH,蛋白都能形成颜色、形貌及"站立性"无明显差别的热诱导凝胶;L-Arg、L-Lys显著提高凝胶弹性、黏聚性、咀嚼性及回复性,降低凝胶硬度和胶黏性,而L-His除降低胶黏性外,对凝胶其他质构特性无显著影响。此外,它们对凝胶持水性提升幅度不大,但能够显著提高凝胶溶胀性,并有效抑制凝胶网络内蛋白浸出,促进蛋白凝胶网络结构的完整化。

Effects of mutation on a new strain Leptospirillum ferriphilum YXW and bioleaching of gold ore

Leptospirillum ferriphilum YXW was isolated through serial dilution from mixed microorganisms enriched in AMD from Dexing copper mine in Jiangxi Province, China. It was mutated by ultrasonic, UV and microwave to collect more efficient strain for bioleaching of gold ore. Physiological and biochemical characteristics indicate that strain YXW is a strict chemoautotrophic microorganism, and the optimal condition for its growth is temperature of 40 °C and pH 1.5. After mutation by ultrasonic, UV and microwave, the density of bacterial cells reached 9×109, 8.4×109 and 4.3×108 mL-1, increased by 291%, 265%and 87%, respectively, compared with the original culture. The bacterial total protein activity was improved by microwave and UV mutations, but was reduced by ultrasonic. Mutations had effects on bioleaching of gold ore in sequence of microwave〉UV〉ultrasonic. During gold ore bioleaching, the bacterial mutant after mutation by microwave had the best effect on the extraction rates of arsenic and iron, which were 19.6%and 17.7%higher than that of the original strain after bioleaching for 10 d, respectively. The results suggested that the effects of mutation on bioleaching of gold ore may not be mainly due to increase of bacterial cells density, but may be mainly attributed to the improvement of bacterial total protein activity.