El-Housseiny Ghadir S, Aboshanab Khaled M, Aboulwafa Mohammad M, Hassouna Nadia A
Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Organization of African Unity St., Abbassia, POB: 11566, Cairo, Egypt.
AMB Express. 2019 Jan 8;9(1):7. doi: 10.1186/s13568-018-0732-y.
Solid-state fermentation has a special advantage of preventing the foaming problem that obstructs submerged fermentation processes for rhamnolipid production. In the present work, a 50:50 mixture of sugarcane bagasse and sunflower seed meal was selected as the optimum substrate for rhamnolipid production using a Pseudomonas aeruginosa mutant 15GR and an impregnating solution including 5% v/v glycerol. Using Box-Behnken design, the optimum fermentation conditions were found to be an inoculum size 1% v/v, temperature 30 °C and unlike other studies, pH 8. These optimized conditions yielded a 67% enhancement of rhamnolipid levels reaching 46.85 g rhamnolipids per liter of impregnating solution, after 10 days, which was about 5.5 folds higher than that obtained by submerged liquid fermentation. Although maximum rhamnolipids concentration was obtained after 10 days of incubation, rhamnolipids concentration already reached high levels (41.87 g/l) after only 6 days. This rhamnolipid level was obtained in a shorter time and using lower carbon source concentrations than most studies reported so far. The findings obtained indicate an enormous potential for employing solid-state fermentation for rhamnolipid production by the studied isolate.
固态发酵具有防止泡沫问题的特殊优势，而泡沫问题会阻碍鼠李糖脂生产的深层发酵过程。在本研究中，使用铜绿假单胞菌突变体15GR和包含5% v/v甘油的浸渍溶液，选择甘蔗渣和向日葵籽粕50:50的混合物作为生产鼠李糖脂的最佳底物。采用Box-Behnken设计，发现最佳发酵条件为接种量1% v/v、温度30°C，与其他研究不同的是，pH值为8。在这些优化条件下，10天后鼠李糖脂水平提高了67%，达到每升浸渍溶液46.85克鼠李糖脂，这比深层液体发酵获得的产量高出约5.5倍。尽管在培养10天后获得了最大鼠李糖脂浓度，但仅6天后鼠李糖脂浓度就已达到较高水平（41.87克/升）。与迄今为止大多数研究报告相比，在更短的时间内且使用更低的碳源浓度获得了该鼠李糖脂水平。所得结果表明，所研究的菌株采用固态发酵生产鼠李糖脂具有巨大潜力。
