Sugar beet molasses bioconversion into biosurfactant: optimization and comparison with other carbon sources

Interest in biosurfactants application has increased considerably due to unique properties, such as diversity, biodegradability and environmentally friendly concerns. Therefore, using abundant and low-cost raw materials and optimizing the biosurfactant production process are economically attractive. In this study, the suitability of sugar beet molasses was compared with some other common carbon sources for rhamnolipids production by Pseudomonas putida KT2440. The effects of different inorganic nitrogen sources, C/N ratios, and incubation time were also investigated to optimize biosurfactant production. The results showed that the maximum biosurfactant precipitated in acetone (5.4 g.L-1) was obtained using molasses and sodium nitrate. In the application of these carbon and nitrogen sources, minimum surface tension was established at C/N ratio of 10 and 8 days of incubation time. Affected by various sources of carbon and nitrogen, the final pH values varied between 2.9 and 8.3. Although the minimum surface tension (41.78 m.Nm(-1)) was measured using olive oil and ammonium chloride, this treatment did not produce the maximum biosurfactant weight. The minimum pH of cell-free supernatants was related to this treatment. In other words, the final pH of the culture medium was effective in measuring parameters related to biosurfactant. Acetone-extracted biosurfactant was pH-dependent and increased with the increasing pH of the culture mediums. The results indicated the potential of sugar beet molasses as a hydrophilic agro-industrial wastes to rhamnolipid production by Pseudomonas putida KT2440.

Automated summary

Interest in the application of biosurfactants has increased due to their unique properties and environmental concerns. In this study, the suitability of sugar beet molasses as a carbon source for biosurfactant production was investigated. The results showed that using molasses and sodium nitrate yielded the highest biosurfactant production. Other factors, such as C/N ratio and incubation time, also played a role in optimizing the production process.