Characterization of scleroglucan fermentation by Sclerotium rolfsii in terms of cell, scleroglucan and by-product, oxalic acid concentrations, viscosity and molecular weight distribution

Scleroglucan is a very viscous, high molecular weight polysaccharide produced by fungi, a group of Sclerotiums. This polysaccharide has a variety of applications due to its structure, ;One of the objectives of this research is to find a way to improve production in scleroglucan fermentation. For the purpose of the research, Sclerotium rolfsii was used as a strain for scleroglucan fermentation since most prior studies have been performed with other strain, Sclerotium glucanicum. First, the general profile of scleroglucan in terms of cell, scleroglucan and by-product, oxalic acid concentrations was derived throughout batch and continuous fermentations. It was concluded that scleroglucan by Sclerotium rolfsii is a growth-associated biopolymer according to the profiles. The microorganism produced oxalic acid at early exponential phase and scleroglucan formation as well as cell growth became active under the acid condition due to the oxalic acid. Second, the C/N molar ratio using glucose and sodium nitrate as carbon and nitrogen sources was examined to find its effect on productivity. This resulted in a higher molar ratio which improved productivity, even though it also increased oxalic acid which is considered waste. A pH of 4.5 led to inferior results to uncontrolled pH or control at 2.5; there were low cell and scleroglucan concentrations and significant amounts of oxalic acid at a pH of 4.5.;Another objective of this study is to measure the molecular weight and viscosity of native scleroglucan solution directly from fermentation broth. The molecular weight of the scleroglucan was measured by a gel filtration chromatograph by directly injecting the fermentation broth. The molecular weight was around ;It was observed that water in the fermentation solution moved to some alcohol solvent through a porous cellulose membrane without any physical assistance. The water transport continued even under resistance by precipitation of the polymer on the membrane wall. It was found that the water transfer into alcohol phases through the porous cellulose membrane was much larger than the opposite case. The water transfer was not driven by pressure. Instead, the transfer occurred by overcoming pressure from the alcohol phases.