Читать книгу Biosurfactants for a Sustainable Future - Группа авторов - Страница 52

Several crops are cultivated primarily for the production of foodstuffs for industries, which are then used in industrial processes that generate byproducts [76, 104, 105]. Go et al. [17] reported that increasing population and growing living standards have contributed to increased demand for edible oils, as they supply the necessary nutritional components and energy for physical activities. Edible vegetable oils are usually composed of triacylglycerols (more than 95%) and various fatty acids [106]. The waste cooking oil/frying oil contains several hazardous chemicals that cause health risks when consumers use it or process it. The composition of the used frying oil depends on the food fried in it and also the number of times it is reused; usually, though, recycled oil has 30% higher polar‐hydrocarbons compared to fresh frying oil [107]. Waste frying oil represents a renewable energy source for the production of new industrial products and alternative feedstock in place of pure and expensive chemicals. Haba et al. [108] studied sunflower oil and olive oil waste for rhamnolipid production by using P. aeruginosa 47T2 (2.7 g/l). They reported 0.34 g/g rhamnolipid production with NaNO₃ (5 g/l) and waste frying oil (40 g/l).

Researchers [109] developed a modified approach of biosurfactant production under submerged culture conditions through Bacillus subtilis MTCC2423 strain using sunflower bran, paddy bran, waste frying oil (50 g/l), yeast extract (5 g/l) and rock salt (1.7 g/l). They observed that the surface tension decreased in glucose + sunflower bran, paddy bran, and frying oils waste by approximately 29.0, 32.0, and 34.5 mN/m, respectively, while glucose produced the best output (2.1 g/l) of surfactin. It was concluded from their results that the surfactin production process was safe for waste disposal and low‐cost biosurfactant development. Pan et al. [110] had also reported rhamnolipids production using P. aeruginosa strain DG30 in fermentation medium enriched with 5% w/v discarded vegetable oil (w/v) and reported 15.6 g/l of biosurfactant during the fermentation process.

Moreover, the coconut fried oil waste (2%) was used by George and Jayachandran [99] for the synthesis of rhamnolipids using P. aeruginosa strain D, with a recorded emulsification index (EI) of 71% and a yield of 3.55 g/l. It was reported that Mucor circinelloides, grown in culture media with 5% waste frying oil, produced ~12.4 g/l of glycolipids [111]. The obtained glycolipids lowered the surface tension by up to 26 mN/m, produced a consistent 129 mm diameter hollow area in the oil dispersal assay, and proved the emulsification capability of up to 65% of crude oil in marine water. All the results reported in this section provide scientific evidence that waste oil has been a good source of carbon to support microbial growth and production of biosurfactants. The waste substrates used for the production of biosurfactants themselves can reduce the cost of production and can be considered environmentally safe by reducing the pollution problem.