Mahamad Siti Syazwani, Mohamed Mohd Shamzi, Radzuan Mohd Nazren, Winterburn James, Zakaria Mohd Rafein
Department of Bioprocess Technology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia.
Institute of Plantation Studies, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia.
Bioprocess Biosyst Eng. 2025 Aug 25. doi: 10.1007/s00449-025-03224-3.
Rhamnolipids (RLs) are glycolipid bio-surfactants produced by microorganisms with applications in industries, including environmental remediation and oil recovery, comparable to chemical surfactants. However, the reproducibility and scalability of RLs production in shake flask systems limit their industrial use, prompting the need for advanced bioreactor systems. This study aims to address this challenge by optimizing RLs production by Pseudomonas aeruginosa RS6 using treated waste glycerol (TWG), a low-cost by-product of biodiesel production, as a carbon source. Response surface methodology (RSM) was employed to evaluate the combined impact of TWG concentration, aeration, and agitation rates on RLs production and microbial behavior within a bioreactor system. Optimal conditions were then determined using central composite design (CCD) and analysis of variance (ANOVA). ANOVA revealed that the quadratic model significantly predicts RLs production (p < 0.0001). TWG concentration significantly influences RLs yield (p < 0.05), while TWG concentration and agitation rates significantly affect biomass production (p < 0.05). Optimal conditions were 2.827% TWG, 1.02 vvm aeration, and 443 rpm agitation. The model's validity was confirmed, yielding 11.32 g/L RLs and 5.38 g/L biomass. Kinetic studies showed Y and Y values of 5.53 g/g and 3.36 g/g, indicating efficient substrate utilization and metabolite production. RSM optimization enhanced RLs yield by 4.88-fold compared to shake flask results. The produced RLs achieved a kerosene emulsion index of 70.12% and reduced surface tension to 28.61 mN/m, highlighting their potential in environmental remediation. This study addresses the scalability issues in RLs production, and highlights the feasibility of using waste glycerol for large-scale RLs production.
鼠李糖脂（RLs）是微生物产生的糖脂类生物表面活性剂，在包括环境修复和石油开采在内的工业领域有应用，可与化学表面活性剂相媲美。然而，摇瓶系统中鼠李糖脂生产的可重复性和可扩展性限制了其工业应用，因此需要先进的生物反应器系统。本研究旨在通过优化铜绿假单胞菌RS6利用处理后的废甘油（TWG，生物柴油生产的低成本副产品）作为碳源来生产鼠李糖脂，以应对这一挑战。采用响应面法（RSM）评估生物反应器系统中TWG浓度、通气量和搅拌速率对鼠李糖脂生产和微生物行为的综合影响。然后使用中心复合设计（CCD）和方差分析（ANOVA）确定最佳条件。方差分析表明，二次模型能显著预测鼠李糖脂的产量（p < 0.0001）。TWG浓度对鼠李糖脂产量有显著影响（p < 0.05），而TWG浓度和搅拌速率对生物量生产有显著影响（p < 0.05）。最佳条件为2.827%的TWG、1.02 vvm的通气量和443 rpm的搅拌速率。该模型的有效性得到了证实，鼠李糖脂产量为11.32 g/L，生物量为5.38 g/L。动力学研究表明Y和Y值分别为5.53 g/g和3.36 g/g，表明底物利用效率高和代谢产物产量高。与摇瓶结果相比，响应面法优化使鼠李糖脂产量提高了4.88倍。所生产的鼠李糖脂的煤油乳化指数达到70.12%，表面张力降低至28.61 mN/m，突出了其在环境修复中的潜力。本研究解决了鼠李糖脂生产中的可扩展性问题，并强调了使用废甘油进行大规模鼠李糖脂生产的可行性。
