Growth studies of Leuconostoc mesenteroides on corn biomass based substrates

Abstract

Leuconostoc mesenteroides is a well-known industrial producer of extracellular bacterial polysaccharide dextran. The main raw material for industrial cultivation of these microorganisms is molasses. Sucrose of molasses is the main source of carbon and energy for bacteria, as well as a precursor of dextran biosynthesis. It is known that the bacteria of the genus Leuconostoc are heterofermentative microorganisms and are capable to utilize various carbohydrates. The purpose of this study was to evaluate the of the corn biomass based mediumon the yield of bacterial biomass and the concentration of the extracellular polysaccharide.The hydrolyzate is a product of chemo-enzymatic treatment of plant lignocellulosic corn biomass and contains such monosaccharides as glucose, arabinose and xylose. The parameters of the composition of the medium were the concentration of hydrolyzate carbohydrates in the form of reducing substances (RS), the concentration of nitrogen (protein and non-protein), sucrose and the presence of minerals. The parameters of the cultivation process are pH and temperature. According to experimental data, the maximum yield of bacterial biomass (9.3 and 8.5%) were achieved on combined media with a sucrose content of 0.2% and a sodium salt (sodium phosphate), respectively. The highest specific growth rates of microorganisms (0.0840 and 0.0746) are demonstrated on a combined medium with a content of 0.15 and 0.3% inorganic nitrogen, respectively. The highest concentrations of extracellular polysaccharides (0.840 and 0.583%) are formed when magnesium and manganese salts are present in the nutrient medium. The optimal pH level for effective growth s is about 7, and the temperature in the range of 30-35 ° C.