Decolourization of Sugar Beet Molasses Vinasse by Lactic Acid Bacteria - the Effect of Yeast Extract Dosage

Vinasse is the waste product from the production of ethanol that is most loaded with pollutants. Known methods of treating vinasse allow for a reduction in the pollution load, but do not remove the brown colour. The aim of this study was to investigate the effect of the addition of yeast extract (YE) on the decolourization of sugar beet molasses vinasse by lactic acid bacteria (Lactobacillus plantarum, L. casei, and Pediococcus parvulus). Experiments were performed in batch mode in a BioStat B bioreactor (working volume of 2 dm(3)) for 72 h at 35.8 degrees C and pH(0) of 6.5. The medium consisted of 25% v/v vinasse, glucose (38.67 g dm(-3)), and different amounts of yeast extract addition (2.24, 4.48, and 8.96 g dm(-3)). It was observed that an increase in the YE dose in the medium was followed by a decrease in decolourization of the vinasse. The maximum decolourization was 28.36% (YE = 2.24 g dm(-3)). Regardless of the YE amount added to the medium, removal of invert alkaline degradation products content in all experiments was at a similar level (approx. 13%). With an increased dose of YE, an increase in the caramel content was observed. The biggest melanoidins removal (62.3%) was found in the process with the highest YE dose. The acrylamide, 4-methylimidazole, furfural, 5-hydroxymethylfurfural, and 2-acetyl-4-(1,2,3,4)-tetrahydroxy-butylimidazole were completely assimilated.