Integration of filtration and liquid-solid process with MN100 resin for corn steep water purification

Corn steep water (CSW) is a secondary stream obtained from corn wet-milling industry that constitutes a source of cost-competitive biocompounds. Among them, biosurfactants are one of the most interesting due to the important industrial applications and the several advantages over commonly used chemical surfactants, such as lower toxicity, higher biodegradability and better environmental compatibility (De et al., 2015). The aim of this work is to study the recovery of biosurfactants from CSW by sequential filtration and liquid-solid extraction with an adsorbent resin such as Macronet MN100 (Purolite). The effect of pH (3, 5 and 7) as well as the amount of resin (0.5, 1 and 2 g) in biosurfactant recovery were evaluated. For that, 10 mL of CSW at 50 g/L were filtered to removed solids and put in contact with different amounts of MN100 resin (pre-conditioned with 1 M HCl and washed with water up to pH 5 during 24 h in continuous rotatory agitation (70 rpm) at room temperature. After this period, the different phases were separated, and the liquid fraction was analyzed by surface tension measurements using a Krüss K20 EasyDyne tensiometer with a 1.9 cm platinum Wilhelmy plate (Germany). The resin, loaded with the biosurfactants, was desorbed with different extractants: hot water, ethyl acetate and methanol with 5% NH3. Results showed a significant increase in the surface tension values (from initial 54 to 65–72 mN/m), which means that MN100 could entrap surface-active compounds from CSW. Under the different conditions assayed, the highest recovery was obtained with the intermediate amount of resin (1 g) and a pH close to neutrality (5). Moreover, the solution of MeOH at 5% NH3 provided the best results for biosurfactant desorption. In conclusion, the integration of filtration and liquid-solid extraction with resins, could be an interesting strategy to recover and purify biosurfactants from CSW.