Pilot-Scale Integrated Membrane System for the Separation and Concentration of Compounds of Industrial Interest from Tortilla Industry Wastewater (Nejayote)

Purpose Evaluation of the performance of a pilot-scale membrane system to separate and concentrate arabinoxylans, hydroxycinnamic acids and fermentable sugars from nejayote. Methods Total suspended solids (TSS) from nejayote were removed by a novel enzymatic process to avoid UF-membrane fouling (Asaff and Reyes 2015; modified to pilot-scale). The free-TSS nejayote was submitted to ultrafiltration and diafiltration processes (5 kDa MWCO polyethersulfone membrane) to separate and concentrate arabinoxylans. Reverse osmosis (cross-linked polyamide membrane) was performed to concentrate hydroxycinnamic acids and fermentable sugars (MW < 5 kDa) from ultrafiltration permeates. Results TSS remotion was highly efficient (final content < 15 ppm). The ultrafiltration permeate flux showed a linear decrease as the °Brix and volume reduction factor (VRF) increased (1.0–2.4). Furthermore, the ultrafiltration membrane, showed the highest rejection (72%) for long-chain arabinoxylans compared to hydroxycinnamic acids and sugars, therefore, their concentration (33.32 g/L) in the retentate was 1.8-fold higher than in the feed. Moreover, arabinoxylans were further purified to 83.2% diafiltering the retentate. In contrast, the reverse osmosis permeate flux decreased exponentially as the °Brix and VRF increased, indicating a fouling phenomenon possibly due to molecular interactions of hydroxycinnamic acids, sugars, and their oligomers with the membrane surface. In this way, their concentrations in the retentate were almost 2-fold higher than in the feed. Conclusion The performance of the pilot-scale integrated membrane system showed that it is a technically feasible method to separate and concentrate compounds of industrial interest from nejayote despite the limitations related primarily to membrane fouling and adsorption of hydroxycinnamic acids. Graphic Abstract