In spite of numerous advantages on operating fermentation at elevated temperatures, very few thermophilic bacteria with polyhydroxyalkanoates (PHAs)-accumulating ability have yet been found in contrast to the tremendous mesophiles with the same ability. In this study, a thermophilic poly(3-hydroxybutyrate) (PHB)-accumulating bacteria (Chelatococcus daeguensis TAD1), isolated from the biofilm of a biotrickling filter used for NOx removal, was extensively investigated and compared to other PHB-accumulating bacteria. The results demonstrate that C. daeguensis TAD1 is a growth-associated PHB-accumulating bacterium without obvious nutrient limitation, which was capable of accumulating PHB up to 83.6 % of cell dry weight (CDW, w/w) within just 24 h at 45 °C from glucose. Surprisingly, the PHB production of C. daeguensis TAD1 exhibited strong tolerance to high heat stress as well as nitrogen loads compared to that of other PHB-accumulating bacterium, while the optimal PHB amount (3.44 ± 0.3 g l(-1)) occurred at 50 °C and C/N = 30 (molar) with glucose as the sole carbon source. In addition, C. daeguensis TAD1 could effectively utilize various cheap substrates (starch or glycerol) for PHB production without pre-hydrolyzed, particularly the glycerol, exhibiting the highest product yield (Y P/S, 0.26 g PHB per gram substrate used) as well as PHB content (80.4 % of CDW, w/w) compared to other carbon sources. Consequently, C. daeguensis TAD1 is a viable candidate for large-scale production of PHB via utilizing starch or glycerol as the raw materials.

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A strain of bacteria CP1 with high nitrogen removal efficiency was newly isolated from the biofilm of a biofilter for removal of NO x from flue gas. The isolate was identified as Pseudomonas aeruginosa based on its physiological and biochemical characteristics and the results of 16S rRNA gene homology analysis. The new isolate had a high denitrifying ability, removing 98.49% of the nitrate in a 24-h period under aerobic conditions, with no nitrite accumulation. With regard to the nitrogen balance, the percentage of nitrogen lost in the flask culture was estimated to be 32.3%, which was presumed to be converted to nitrogen gas. An analysis of its denitrification activity showed that the optimal C/N and temperature were 12 and 30°C-40°C, respectively. By using glucose, sodium citrate and succinate, CP1 removed nitrate with high denitrification efficiency. The change in DO did not influence the effects of denitrification when it varied from 0 to 7.2 mg/L. The results show that CP1 could be a good candidate for the process of aerobic denitrification.

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