Study On Fermentation Biotechnology Of Gellan Gum Production By Halobacterium S. Paucimobilis OHZJUJW And Its Application

Gellan gum was mostly produced from Sphingomonas paucimobilis which has been studied most. During fermentation process, culture medium compositions (carbon source; nitrogen source; inorganic ions;amino acids, etc.) and culture conditions (temperature; initial pH of culture medium; fluid volume; stirring speed; inoculums density; etc) had a significant impact on the properties of gellan gum such as molecular weight; gel property; rheological property and so on. In the study, an endophyte strain that previously isolated from Qinghai Plateau was found to produce gellan gum during the liquid cultivation. The strain was identified to be halobacterium Sphingomonas paucimobilis QHZJUJW by analyzing16SrDNA and morphological properties. And the new method of mutation, Atmospheric and Room Temperature Plasma (ARTP) was used to breed good strain of high yield. And then the cultivation process and technology of gellan gum producing strain were fully discussed. At last, rheological properties of gellan gum and its application were researched. The primary results of this research were as follows:(1) Screening and indentification production of strain. In the study, an endophyte good strain that isolated from Qinghai Plateau was found to produce exopolysaccharides (EPS) during the liquid submerged cultivation. The strain was identified to be halobacterium S. paucimobilis QHZJUJW by16SrDNA and morphological properties analysis.(2) The new method of mutation, Atmospheric and Room Temperature Plasma (ARTP) was used to modify halobacterium Sphingomonas paucimobilis QHZJUJW. Then though selective screening using nutrient agar (LB) plates containing100mg/L ampicillinon and continuously culturing in the liquid fermentation, the strain302which has a good ability to produce gellan gum was screened. The production level of18.0g/L gellan gum had already reached beyond medium degree, increased by20.0%contrasting with the original strain.(3) One-factor-at-a-time was used to screen the preferable nutriments (carbon sources, nitrogen sources) for gellan gum production. Then, response surface methodology was applied to optimize the cultivation medium of halobacterium S. paucimobilis QHZJUJW, and the conditions of cultivation were also studied. Based on the experimental results, the optimal culture medium for producing gellan gum was composed of40.00(w/v) sucrose,3.00%peptone (w/v), MgSO4(w/v),9.20%KH2PO4(w/v),7.50%Na2HPO4(w/v),4.30%K2SO4(w/v), pH6.8-7.0. The maximal gellan gum was19.89±0.68g/L, which was agreed closely with the predicated value (20.12g/L). the optimum conditions were as follows:the initial pH was7.0, the optimal inoculated time was16-24h, the liquid volume was50mL, the inoculation amount was10%. It had laid the foundation and had a industrial significance of halobacterium S. paucimobilis QHZJUJW.(4) The purification was used to detect extracellular polysaccharide (EPS) produced from halobacterium S. paucimobilis QHZJUJW. The detection methods include Ultraviolet spectrum (UV), Infrared spectrum (IR), Nuclear magnetic resonance (NMR), Raman spectroscopy (SERS) and Atomic force microscope (AFM). We preliminarily concluded that extracellular polysaccharide (EPS) from S. paucimobilis QHZJUJW was gellan gum.(5) Rotated rheometer was used to test the rheological properties of several different gellan gum and xanthan gum. And through the comparative analysis, the rheological properties of several gum were similar. Focusing on the research of application of noodles, the rheological properties of flour were first studied, the flour was added different concentration of gum. Then the TPA indicators were analyzed to reach the conclusion that gellan gum played a a good performance in noodles making.