Pilot-scale nanofiltration vibratory shear enhanced processing (NF-VSEP) for the improvement of the separation and concentration of compounds of biotechnological interest from tortilla industry wastewater (nejayote)

Abstract

The aim of the present work was to evaluate the performance of a pilot-scale nanofiltration vibratory shear enhanced processing (NF-VSEP) coupled to an enzymatic/flocculating system to recover, separate, and concentrate compounds of biotechnological interest contained in nejayote, such as arabinoxylans (AXs), hydroxycinnamic acids and reducing sugars (RS). Enzymatic starch granules hydrolysis, flocculation of remaining suspended particles and microfiltration pretreatments resulted in a robust, reproducible, and efficient technologies to completely remove total suspended solids (TSS) from nejayote. The free-TSS nejayote was submitted to the first NF-VSEP module (annular flat sheet polyethersulfone membranes, 1,000 Da MWCO) to separate and concentrate long-chain AXs. At the end of the process, a volume reduction factor (VRF) of 7.4 was achieved, increasing the AXs concentration in the retentate stream by 3.4-fold (37.67 g/L). The permeate stream resulting from this first operation was subjected to a second NF-VSEP module (annular flat sheet composite polyamide membranes, 150 Da MWCO) to concentrate hydroxycinnamic acids, AX oligomers and RS. The permeate flux and retentate conductivity increased almost linearly as the VRF increased (1–5.5). At the end of the process (VRF 5.5), the concentrations of AX oligomers, hydroxycinnamic acids and RS in the retentate stream were greater than 3-fold than those in the initial feed. The resulting permeate stream was water with a minimal organic material content that can be reused in the process or disposed of in an environmentally friendly manner. The performance of the integrated pilot-scale NF-VSEP reveals a robust, efficient, and improved system to recover, separate and concentrate high biotechnology interest compounds from nejayote, overcoming serious limitations (fouling and fast permeate flux decline) present in static systems. The experimental data presented here set the standard for further industrial scaling to expand the value chain and guarantee the circular economy and global sustainability of the tortilla industry.