Distillery wastewater decolorization by Lactobacillus plantarum MiLAB393

Abstract

Sugar beet molasses vinasse is a high-strength distillery wastewater. It contains colored substances which significantly affect the degree of pollution and toxicity of vinasse. This study aimed to optimize the medium composition and the process condition of sugar beet molasses vinasse decolorization by Lactobacillus plantarum MiLAB393. The research was conducted in two stages: the shake-flask stage in the 250 cm3 Erlenmeyer flasks and the batch experiments in the 5 dm3 working volume stirred-tank bioreactor. During the study, the concentrations of glucose and yeast extract were optimized using experimental design of experiments (DOE). The influences of the initial value of pH and pH control, temperature, stirrer speed and glucose concentration on decolorization were tested. The highest color reduction of 24.1% was achieved for an experiment in which 24.93 g/dm3 of glucose was added to the medium and stirrer speed was 200 rpm. This efficiency of 30% v/v sugar beet molasses vinasse decolorization was obtained at non-controlled pH 6.0 and at 35.8°C. It was found that pH control determines vinasse decolorization. When the pH was controlled, decolorization did not exceed 9%. The glucose and yeast extract concentration and the stirrer speed have a great influence on the process. Changes in these parameters may increase biomass growth while decreasing the decolorization.