Production of D-lactic acid by L. delbrueckii growing on orange peel waste hydrolysates and model monosaccharide solutions: effects of pH and temperature on process kinetics

Abstract

D-lactic acid is a key monomer of polylactic acid (PLA) and other biopolymers. In this work, the effects of temperature and pH on the D-lactate production with Lactobacillus delbrueckii in model sugar solutions and real orange peel waste hydrolysates (OPWH) have been studied and modeled with a non-structured non-segregated kinetic model. Lactobacillus delbrueckii ssp. delbrueckki CECT 286 yields 0.88 g/g of D-lactate (purity 97%) with a productivity of 2.56 g/L·h in the best tested conditions (40 °C and pH 5.8). The proposed kinetic model is able to describe the performed runs, and its kinetic parameters reflect the influence of temperature and pH on the uptake of monosaccharides, D-lactic acid production, and bacterium growth. Moreover, it can be applied to simulate runs with real OPWH supplemented with MRS broth or corn steep liquor (CSL) as a nitrogen source.