产鼠李糖脂菌株种子培养条件和C、N源的优化

对自行筛选的3个可利用废弃油脂进行发酵生产鼠李糖脂的铜绿假单胞菌菌株进行评价,并进行了种子培养条件和摇瓶发酵部分条件的优化。种子培养优化实验表明,当培养基pH 6～8,培养温度为30 ℃时最利于菌体生长。菌株均具有一定的耐盐性,在5%的盐度下生长未受到明显抑制,因此在沿海地区采用盐水或海水发酵具有较广阔的应用前景。通过排油圈、表面张力、苯酚-H2SO4比色法比较了这3个菌株的表面活性剂表面活性的大小,以表现较好的Z41进行了摇瓶发酵条件的优化。单因素实验表明,发酵较优条件为发酵温度30 ℃,接种量5%。在此基础上,通过正交试验对Z41菌株发酵培养基中的C、N源进行了研究,实验结果表明,在考虑因素间交互作用和发酵成本的情况下,最佳C源为3%炸货油,最佳N源为3.5 g/L尿素。在此发酵条件下,糖脂产量较高13.024 g/L,且成本较低。

Optimization of seed culture, carbon and nitrogen conditions of rhamnolipid producing stains

Three Pseudomonas aeruginosa strains which could use waste oil for production of rhamnolipid were evaluated and the optimization of seed culture conditions and some parameters of shaking flask fermentation conditions were conducted. It was found that the optimum growth conditions in nutrient broth were 30 ℃and pH 6-8. The three strains showed the resistance to the saline stress at the concentration of 5 %, indicating good potential to be employed as saline water or sea water fermentation strains in coastal areas. Meanwhile, their biosurfactant producing capacities of three strains, i.e. , Z1, Z41 and Z49 were assessed by oil spreading, surface tension measurement and phenol-sulfuric acid colorimetric methods. By comparison, Z41 performed best in bio-surfactant producing capacity and was chosen as the strain for fermentation conditions optimization. Single factor experiments showed that optimal fermentation temperature was 30℃ and inoculation amount was 5%. The results of orthogonal experiment of 7141 showed that considering the fermentation cost, the optimal carbon source type and amount were waste edible oil and 3%, and the optimal nitrogen source type and amount were urea and 3.5 g/L. Under these conditions, glycolipid yield reached 13. 024 g/L with low cost.