Waste Viscose for Optically pure Lactic acid Production

Abstract

Recycling of textile fibers is a mandatory step in the life-cycle of fabrics to avoid incineration or landfilling. After fiber-to-fiber recycling, cellulose fiber saccharification opens the door to the production of biochemical building blocks through microbial fermentation. This study documents for the first time the production of optically pure D-lactic acid (D-LA), one of the precursors of polylactic acid (PLA), from post-consumer waste viscose. Enzymatic hydrolysis was applied to white and colored waste viscose to produce two glucose-rich solutions that were used as carbon source for the genetically modified Pediococcus acidilactici ZP26. Afterward, batch and fed-batch cultivations were conducted with very similar results for the control and both waste viscose hydrolysates (white and colored). The strain was able to produce D-LA without any signs of inhibition by possibly toxic compounds present in the recycled textiles (additives, dyes, and other contaminants). The highest D-LA concentration and yield was reached in the batch reactors with colored waste viscose at 42.4 g/L and 0.97 g/g, respectively. In the fed-batch cultivations, the best result was achieved with the white waste solution, with 59.5 g of D-LA (40.8 g/L), and a yield on total glucose of 0.70 g/g. Notwithstanding the need for more research in the utilization of saccharified waste viscose as carbon source for bioprocesses, this is an important proof of concept of an application of streams from tertiary recycling of cellulosic fibers in the production of platform biochemicals. Graphical Abstract