Production of exopolysaccharide (EPS) from a strain of Bacillus polymyxa was studied. Sucrose and potassium nitrate were found to be efficient carbon and nitrogen sources, respectively, for the production of the EPS. EPS production increased with the increase of sucrose concentration, probably due to the facilitated carbon uptake. Optimal pH was 7-8, and a sufficient supply of oxygen was needed for the EPS production. It was noted that the EPS synthesis by this B. polymyxa was growthassociated, indicating that a sufficient supply of nutrients was required for a high production of the EPS. As high as 54 g/l of EPS with a yield of 63% (g EPS/g sucrose) was obtained in 48 h of fed-batch cultivation with intermittent feeding of sucrose and potassium nitrate.
Production of poly(~/-hydroxybutyrate-co-//-hydroxyvalerate) [poly (ltB-co-tlV)] in Alcaligenes eutrophus NCIMB 11599 was investigated at various concentrations of valerate. With valerate, higher specific production rate, yield, and IIV content of the copolymer were obtained than those with propionate.By feeding valerate in the copolymer accumulation stage, a product titre as high as 90.4 g/I with ttV content of 20.4 °/6 could be obtained in 50 hi" of fed-batch operation.
A variety of physical, chemical, and microbiological techniques have been developed to deal with soil and groundwater contamination. However, in the presence of the large portion of soil micro-environments, contaminant rebound and/or tailing have been frequently reported. Case study of total petroleum hydrocarbons (TPH) removal by full-scale land farming showed that contaminant rebound and/or tailing occurred in 9 out of total 21 cases and subsequently resulted in problems of a long term operation to satisfy TPH guidelines of contaminated soil and groundwater. The main cause of contaminant rebound and tailing is considered to be the strong interactions between contaminants and micro-environments including micro-particles, micro-pores, and organic matter. Thus, this study reviewed the effects of soil microenvironments of soil and groundwater on the removal efficiency for both heavy metals and petroleum contaminants. In addition, the various methods of sampling, analysis, and assessment of soil micro-environments were evaluated. Thorough understanding of the effects of soil micro-environments on contaminant removal will be essential to achieve a costeffective and efficient solution to contaminated sites.
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