Asian Journal of Biotechnology and Bioresource Technology

Lactic acid is considered a type of produce of wide industrial application; has high reactivity, thus expanding its possibilities of use. Lactic acid synthesis is possible from the fermentation of residual and renewable raw materials, being the economically viable process.

Aims: This study is aimed to investigate lactic acid production from the sorghum bagasse fermentation, through the conversion of xylose contain in the hemicellulose by Lactobacillus pentosus using experimental statistical design.

Study Design: Initially, a synthetic adapted medium was evaluated for fermentation assays after cell activation and propagation. The screening for parameters that influence lactic acid SSF production has been done through factorial design. The desirability function was verified and statistically validated.

Place and Duration of Study: this research was carried out at Department of Biochemical Engineering, School of Chemistry/ Federal University of Rio de Janeiro, Rio de Janeiro, RJ, 21249-900, Brazil. The study will lasted from 2016 to 2018.

Methodology: For the SSF production, the hemicellulose acid pretreatment conditions were as follows: 1.39% (v/v) H₂SO₄ concentration, 1:4 solid:liquid ratio, 52 g.mL^-1 and 46.7min at 121ºC. Subsequently, 2% (v/v) and 10% (v/v) cells in the hydrolyzate, 50% (v/v) and 100% (v/v), respectively, were added under anaerobic conditions, 120 rpm orbital agitation in a shaken flasks and in a instrumented bioreactor. Then, the statistical analysis was used for following independent variables evaluation: inoculum, xylose concentration and KH₂PO₄ concentration, add to the complementary hemicellulose hydrolyzate medium.

Results: The onepot fermentation steps using xylose synthetic medium promoted the production of Lactic Acid, 21 g/L, volumetric productivity (Q_P) of 0.59 g/L.h and 0.583 g/g. The main results obtained was Lactic Acid, 30g/L, under the condition of 50%, hemicellulose hydrolyzate from sorghum, without detoxification, reaching 1.25 g/L.h volumetric productivity.

Conclusion: The results were very promising using an agro-industrial residue. The optimization of cultivation conditions in a chemically defined medium enabled the development of the best growth conditions and reduction the use of potassium phosphate.