Distillery wastewater decolorization by Lactobacillus plantarum MiLAB393

Abstract

2014), yeast (Tiwari et al. 2014, Mahgoub et al. 2016) and bacteria (Santal et al. 2016, Boopathy and Senthilkumar 2014) for color removing. Because of high pollution loads, many researchers treat vinasse before decolorization. The vinasse is centrifuged, fi ltered or anaerobically treated (Tiwari and Gaur 2014, Boopathy and Senthilkumar 2014, Tondee and Sirianuntapiboon 2008, Ravikumar et al. 2013). Other researchers did not use wastewater from distilleries but synthetic melanoidins, which are easier to decolorize (Agnihotri 2015, Santal et al. 2016). In our study we used sugar beet molasses vinasse without pretreatment. Moreover, this kind of wastewater has not been tested by other researchers because they have focused on cane vinasse (Espana-Gamboa 2015, Shukla 2014). The aim of our study was to optimize the medium composition and the process conditions of sugar beet molasses vinasse decolorization by Lactobacillus plantarum MiLAB393. The optimization of the concentrations of glucose and yeast extract using experimental design (DOE) was made at the stage of shake-fl ask cultures. During the batch experiment, the Abstract: Sugar beet molasses vinasse is a high-strength distillery wastewater. It contains colored substances which signifi cantly aff ect 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-fl ask stage in the 250 cm 3 Erlenmeyer fl asks and the batch experiments in the 5 dm 3 working volume stirred-tank bioreactor. During the study, the concentrations of glucose and yeast extract were optimized using experimental design of experiments (DOE). The infl uences 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/dm 3 of glucose was added to the medium and stirrer speed was 200 rpm. This effi ciency 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 infl uence on the process. Changes in these parameters may increase biomass growth while decreasing the decolorization.