Evaluation of biosurfactant production from various agricultural residues by Lactobacillus pentosus

The cost of biosurfactant production may be significantly decreased by using inexpensive carbon substrates like agricultural residues. However, scarce information can be found in the literature about the utilization of lignocellulosic residues for obtaining biosurfactants. Usually agricultural residues are field burned, producing various toxic compounds to the atmosphere; so, as an interesting alternative to the traditional field burning of this kind of residue, this work proposes the utilization of agricultural wastes (barley bran, trimming vine shoots, corn cobs, and Eucalyptus globulus chips) for simultaneous lactic acid and biosurfactant production. Previous to this biotechnological process, lignocellulosic residues were hydrolyzed, using H2SO4, under selected conditions and neutralized with CaCO3. Following, Lactobacillus pentosus was employed for the fermentation of hemicellulosic hydrolyzates after nutrient supplementation. Biosurfactants were measured by taking into account the surface tension reduction. The highest value of reduction (21.3 units) was found when using hemicellulosic sugar hydrolyzates obtained from trimming vine shoots, corresponding to 0.71 g of biosurfactant per g of biomass and 25.6 g of lactic acid/L. On the contrary, barley bran husk hydrolyzates only produced 0.28 g of biosurfactant per g of biomass and 33.2 g of lactic acid/L. The differences between biosurfactant production can be attributed to the different compositions of the hydrolyzates.