OPTIMIZATION OF CULTURE MEDIUM FOR MICROBIAL BIOSURFACTANTS PRODUCTION

RIVERO, MARIANO; SANGUINO-JORQUERA, DIEGO GASTÓN; DIEDRICH, EMILIA; IRAZUSTA, VERÓNICA

Congreso; XVIII Congreso Argentino de Microbiología General, SAMIGE 2022; 2022

Sociedad Argentina de Microbiología General

Surfactants are amphipathic molecules with surface-active action mainly used in the pharmaceutical, food, cosmetic and cleaning industries. When these molecules are produced by microorganisms, they are called biosurfactants. These have several advantages over their synthetic counterparts. However, high production costs limit its market. One option to reduce the cost is to use agro-industrial by-products like black liquor (BL) and vinasse (V) as economic substrates.This work aimed to identify microorganisms isolated from V and BL and optimize their biosurfactant production, using V or BL as medium components.For the identification DNA was extracted from five selected strains. The genes encoding 16S and 18S rRNA were amplified by conventional PCR, using universal primers in a thermocycler. The amplification products were sequenced by Macrogen (Seoul, South Korea). Gene sequences were analyzed with Chromas and aligned by using Clustal W 1.74, followed by the construction of a neighbor-joining phylogenetic tree (MEGA4). Nucleotide sequences were analyzed by BLAST and compared to the GenBank database for partial identification, where they were uploaded.Factorial designs of two factors at two levels (2 2 ) and a central point, measuring two responses in triplicate, were run. The factors selected were substrate composition (SC) and production time. The SC was 5% V, 5g/l nutrient broth (NB), 12.5 g/l olive oil (O) at a high level (H) or 1% V, 1g/l NB, 2.5 g/l O at a low level (L) for acidophilic strains and 5% BL, 5g/l NB, 11.5 g/l O at H or 1% BL, 1 g/l NB, 2.3 g/l O at L for alkaliphilic strains. The production times were 24, 48, 72 and 96 h for both groups. The responses were the optical density (OD) and decreased surface tension (ST) of the supernatant from the sterile medium (ΔST) using the ADSA technique. Analysis of variance (ANOVA) was used to determine the significance (Design Expert version 11.0).Five bacterial strains were identified: a1: Lactobacillus paracasei, a5: Lactobacillus rhamnosus, b1: Bacillus safensis, b2: Alkalihalobacillus halodurans and one yeast, a6: Pichia cecembensis.The optimum ΔST (p <0.05) and SC corresponding for each strain was: a1=14.93 mN/m at SC L, a5=13.66 mN/m at SC H, a6=11.69 mN/m at SC HL (high or low level), b1=27.20 mN/m at SC HL and b2=16.91 mN/m at SC H. The optimum values were at 48 h of production for all the strains. Regarding OD (p <0.05), alkaliphilic strains reached greater values (OD 600nm = 4 - 7) than the acidophilic ones (OD 600nm = 0.35 - 2.6). Industrial by-products such as V and BL can be used in the formulation of culture media for biosurfactant production. In this work, acidophilic and alkaliphilic strains were successfully tested by factorial designs, and both Bacillus sp. b1 and Lactobacillus sp. a1 were identified as a strains with great potential for the production of biosurfactants.