USAGE OF BY-PRODUCTS FROM SUGAR INDUSTRY AS A CHEAP SUBSTRATE FOR DEXTRANSUCRASE PRODUCTION Different treatments of sugar beet pulp for enhanced dextransucrase production on molasses

Abstract

Dextransucrase (DS) is extracellular enzyme that catalyses the synthesis of dextran using sucrose as a substrate, mainly produced by microorganisms belonging to the genera Lactobacillus, Leuconostoc and Streptococcus. The aim of this study was usage of byproducts from sugar refineries, molasses and sugar beet pulp (SBP) as a cheap substrate for DS production. Fermentation process was performed by a natural isolate from water kefir grain Leuconostoc mesenteroides T3. Molasses (ethanol Factory Alpis, Kovin, Serbia) with addition of SBP (Fibrex 620, Nordic Sugar, Denmark) was used as fermentation media. Molasses was diluted in distilledwater to a concentration of 2.5%. SBP was grounded in a mortarand pestle to a particle size of 500–800μm. Four different treatments were performed on the SBP before it was added into molasses: NaOH extraction, enzymatic pretreatment (Viskozym), biological pretreatment (Paenibacillus chitinolyticus CKS1) and combination of microwave and ultrasound treatment. The enzyme activity was determined by measuring the concentration of released reducing sugars by DNS method at 540nm, using fructose as a standard.Combination of microwave and ultrasound treatment as well as biological pretreatment resulted in low DS activity. The best results of 1.45U/ml were obtained with alkali and enzymatic pretreatments. Considering that enzymatic treatment is environmental friendly it provides suitable method for SBP pretreatment for enhanced DS production on molasses.