Lactic acid production from xylose: an alternative use for pentose from sugarcane hydrolyzed bagasse

Full implementation of 2G-ethanol production still has bottlenecks to be overcome. An important one is that the most used microorganisms aren’t able to consume pentose from bagasse hydrolysis. Processing it is crucial in the economic viability for the production of 2G-ethanol, and cannot be passed up. Many efforts have been made in the utilization of pentose, including genetic modification of microorganisms to use it as carbon source to produce molecules of interest. However, use of GMO in large-scale processes may represents problems, from public to environmental concerns together with costs. Thus, this work presents an alternative route for the use of xylose from hydrolyzed bagasse, producing lactic acid without the use of GMO. Lactic acid besides a valuable chemical may be considered a platform for other chemicals. Sugarcane bagasse was submitted to a hydrothermal pre-treatment with sulfuric acid in order to obtain a xylose's liquor with low concentration of inhibiting molecules. Fermentations were performed using Lactobacillus plantarum (37°C, 24 hours). The culture medium selected was composed by 50g/L of fermentable sugars from hydrolyzed bagasse non-detoxified (≈78% xylose, 22% glucose), 20g/L of yeast-extract, and 5g/L of sodium acetate. The final lactic acid yield was 53% and the productivity was 0.9gL^-1h^-1. Lb. plantarum is able to consume hemicellulosic hydrolysate without detoxification, which is very attractive in terms of robustness for an industrial process, especially in partnership with ethanol industry. Although aromatic inhibitors affect negatively productivity and yield, what requires process improvements, xylose was satisfactorily consumed showing the potential of the proposed approach.