Anaerobic production of extracellular polysaccharide by Butyrivibrio fibrisolvens strain nyx
Abstract
Effective aeration is a challenge for industrial production of extracellular polysaccharides (EP). Anaerobic bacteria would eliminate the need for aeration. Conditions which support EP production by gastrointestinal tract anaerobes have also not been thoroughly described. Anaerobic production of EP was examined, using a previously uncharacterized, obligately anaerobic rumen isolate, strain nyx. Early results suggested that nyx was Butyrivibrio fibrisolvens. The main objectives were to: characterize the EP; verify that strain nyx was B. fibrisolvens; determine nutritional requirements and conditions which promoted EP production; describe growth and EP production kinetics. Strain nyx was grown anaerobically in defined media. Based on the chemical and rheological results, it was concluded that nyx produced EP which consisted mainly of carbohydrates, and which was rheologically similar to xanthan gum. Strain nyx was identified as B. fibrisolvens, based on gram stain, morphology, nutrition, fermentation products, and EP composition. In addition to carbohydrate and nitrogen sources, nyx required acetate, folic acid, biotin, and pyridoxamine. Strain nyx produced similar amounts of EP at 35$\sp\circ$C to 42$\sp\circ$C. Strain nyx utilized ammonium sulfate, urea, or vitamin free case in hydrolysate (VFCH) as nitrogen sources for growth and production of EP. On the basis of nitrogen content, ammonium sulfate was the most readily available, followed by urea and VFCH. Additional nitrogen resulted in higher growth and EP production, while excess nitrogen had little additional effect. The highest levels of ammonium sulfate and VFCH supported similar rates of growth and EP production. Of carbohydrates tested, glucose supported the fastest growth and most EP production, followed by sucrose, xylose, and lactose. Xylose supported almost as much growth, but about half the EP production, compared to glucose. Increasing acetic acid improved growth and EP production, while excess acetic acid had little additional effect. With noted exceptions, conditions that promoted growth also promoted EP production. Strain nyx produced EP during active growth, and not during stationary phase. During exponential growth, EP production was also exponential.
Degree
Ph.D.
Advisors
Patterson, Purdue University.
Subject Area
Microbiology
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