Screening of medium components and process parameters for sugar beet molasses vinasse decolorization by Lactobacillus plantarum using Plackett-Burman experimental design

Abstract

Sugar beet molasses vinasse is characterized by a high COD and dark brown color produced by three groups of colorants: melanoidins, caramels, and invert degradation products of alkaline hydrolysis. These environmental pollutants have to be effectively removed via biodegradation processes before discharge into a watercourse. The aim of this study was to assess how the type of the bacterial culture used (static or agitated), and the addition of nutrients (wheat stillage, MgSO4·7H2O, (NH4)2SO4, KH2PO4, yeast extract, glucose, fructose, sucrose, and peptone) contribute to the effectiveness of sugar beet molasses vinasse decolorization with Lactobacillus plantarum. The Plackett-Burman experimental design was used to reduce the number of experiments. Decolorization of nutrient-enriched vinasse (25% v/v) was performed at an initial pH of 6.25 and 37°C for 7 days. Color was measured spectrophotometrically at 475 nm. Concentrations of sugars, organic acids, and colorants were determined by HPLC. The nutrient was screened when the probability value exceeded 95% of the confidence level. 67% efficiency of decolorization of sugar beet molasses vinasse by L. plantarum was obtained. The type of bacterial culture and the addition of wheat stillage, yeast extract, glucose, peptone, and (NH4)2SO4 were significant factors for the decolorization process.