ABSTRACT
12 strains of H2-producing bacteria were isolated and purified from anaerobic sludge, aerobic sludge and river bottom sludge by Hungate method. A new species of high efficient hydrogen production bacterium Enterococcus sp. LG1 (registration number: EU258743 ) was studied deeply. It was showed that the Enterococcus sp. LG1 was an anaerobic and Gram-negative bacterium. Sequence analysis of this type of clones showed that it was affiliated with the genus Enterococcus and it was not reported yet in other paper at present. Meanwhile, batch tests of anaerobic fermentative hydrogen production by Enterococcus sp. LG1 were investigated by using sterilization pretreated sludge as substrate. The changes of soluble COD, protein, carbohydrate and pH value during hydrogen fermentation were monitored. It was found that only hydrogen and carbon dioxide were produced by this strain and no methane was detected during fermentation. The maximal hydrogen yield was 36.48 mL/g TCOD and the hydrogen concentration in the gas phase was 73.5%. The Enterococcus sp. LG1 was a butyrate fermentation bacteria analyzed by metabolites.
ABSTRACT
<p><b>OBJECTIVE</b>To isolate the bioflocculant-producing bacteria from activated sludge and investigate the flocculating characteristics of the newly isolated bioflocculant.</p><p><b>METHODS</b>Bacteria were screened from activated sludge samples to isolate bioflocculant-producing bacteria. Flocculating activity was used as a measure of the flocculating capability of the bioflocculant.</p><p><b>RESULTS</b>A novel bioflocculant-producing bacterium was isolated, which was identified to belong to genus Aeromonas and named as Aeromonas sp. N11. Flocculating activity increased in the presence of K+, Na+, or Ca2+. The highest flocculating activities for kaolin suspension were obtained in acidic pH ranges, and optimum pHs for it were 3.0, 4.0, and 5.0 with 1 mmol/L K+, Ca+, and Na+ present, respectively. The highest flocculating activities for soil suspension were observed at pH 8.0. The bioflocculant had a good flocculating activity and could achieve a flocculating activity of 92.4% for kaolin suspension at a dosage of only 1 mgxL(-1), and its activity in kaolin suspension was decreased by only 9.2% after heating at 100 degrees C for 60 min.</p><p><b>CONCLUSION</b>The bioflocculant produced by Aeromonas sp. N11 has strong flocculating activity and high stability, which affords high possibility of its practical use.</p>