Optimization of biosurfactant and bacteriocin-like inhibitory substance (BLIS) production by Lactococcus lactis CECT-4434 from agroindustrial waste

The use of low-cost substrates and wastes as fermentative media is a simple strategy for overcoming excessive production costs of bioactive molecules and to make the process more profitable. In this context, the aim of this work was to optimize the production of biosurfactant by Lactococcus lactis CECT-4434 from whey and vinasse from industrial sources. For this purpose, a 24 central composite design (CCD) was proposed to maximize biosurfactant production. Besides, the ability of Lc. lactis to synthesize bacteriocin-like inhibitory substance (BLIS) was also evaluated, therefore contributing to the profitability of the biotechnological process. Results showed that whey at 15% positively influenced biosurfactant production (on average 8.9 mg/L), reducing surface tension by about 18.1 mN/m. Molecular composition of the biosurfactant was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance which confirmed the presence of carbohydrates, lipids and proteins, defining this molecule as a glycolipopeptide. Regarding the BLIS synthesis, the highest concentration of sucrose (2.0%) and the lowest vinasse level (1.0%) reduced the production of BLIS identified by the decrease in antimicrobial activity (mean inhibition zone of 10.7 mm). Conversely, the lowest sucrose concentration and highest vinasse level exerted the strongest inhibition, with a mean inhibition zone of 12.2 mm against Staphylococcus aureus CECT-239.