Removal of nitrogen by Antarctic yeast cells at low temperature

Nitrate removal in a medium (at 5°C ) and the effect of culture temperature on the fatty acid composition were investigated using Candida sp. which was isolated from the upper layer of Lake Vanda in the McMurdo Dry Valleys, Antarctica. The strain was cultured at 5°C aerobically, on a synthetic medium containing potassium nitrate (NO_3-N, 100 mgl^) as a nitrogen source, and examined the effects of pH and chlorine on growth and NO_3-N removal in the medium. Within the pH of 3 to 7 the yeast cells exhibited a similar removal of nitrate level. The strain grew well and also removed nitrate at chlorine concentrations of 5 and 10 mgl^ but did not grow at chlorine concentration of 20 mgl^. Decreasing the growth temperature induced an increase in the content of linolenic acid (18:3) in the yeast cells

Mathematical Model of Organic Substrate Degradation in Solid Waste Windrow Composting

Organic solid waste composting is a complex process that involves many coupled physical, chemical and biological mechanisms. To understand this complexity and to ease in planning, design and management of the composting plant, mathematical model for simulation is usually applied. The aim of this paper is to develop a mathematical model of organic substrate degradation and its performance evaluation in solid waste windrow composting system. The present model is a biomass-dependent model, considering biological growth processes under the limitation of moisture, oxygen and substrate contents, and temperature. The main output of this model is substrate content which was divided into two categories: slowly and rapidly degradable substrates. To validate the model, it was applied to a laboratory scale windrow composting of a mixture of wood chips and dog food. The wastes were filled into a cylindrical reactor of 6 cm diameter and 1 m height. The simulation program was run for 3 weeks with 1 s stepwise. The simulated results were in reasonably good agreement with the experimental results. The MC and temperature of model simulation were found to be matched with those of experiment, but limited for rapidly degradable substrates. Under anaerobic zone, the degradation of rapidly degradable substrate needs to be incorporated into the model to achieve full simulation of a long period static pile composting. This model is a useful tool to estimate the changes of substrate content during composting period, and acts as a basic model for further development of a sophisticated model

NITRATE REMOVAL BY ANTARCTIC PSYCHROPHILIC YEAST CELLS UNDER HIGH SALT CONDITIONS (19th Symposium on Polar Biology)

We researched nitrate removal in water with high salt concentrations at low temperature using Candida sp. which was isolated from the upper layer of Lake Vanda in the McMurdo Dry Valleys, Antarctica. The strain was cultured in a synthetic medium that contained nitrate as the sole nitrogen source The time course for the growth, and the nitrate and the total organic carbon (TOC) removals were examined aerobically in the presence of 0-20% NaCl at 5℃. The effects of pH and the C/N ratio on the removal of nitrate were studied Candida sp. can remove more than 90% of nitrate up to an NaCl concentration of 10% in the medium As compared with 0% NaCl, 4% NaCl in the medium did not influence the growth rate and the removal of nitrate and TOC, but, at NaCl of 8 and 10%, the growth and removal of nitrate and TOC were decreased slightly. The yeast did not grow in the medium that contained NaCl of 15 and 20%. At pH of 3 to 7, yeast cells exhibited a similar removal nitrate level but it decreased at pH 1 and 2 The removal of nitrate increased with an increase in the C/N ratio and the nitrate in the medium was completely removed at a C/N ratio of 40. Nitrite was not observed in the cultured broth throughout the experiments The ammo acid composition of the yeast cells did not change with nitrogen sources