Duangporn Kantachote

Effects of long-term contamination of DDT on soil microflora with special reference to soil algae and algal transformation of DDT.

DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) and its principle metabolites, DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene) and DDD (1,1-dichloro-2,2-bis(p-chlorophenyl)ethane) are widespread environmental contaminants but little information is available concerning their effects on non-target microflora (especially microalgae and cyanobacteria) and their activities in long-term contaminated soils. For this reason a long-term DDT-contaminated soil was screened for DDT residues and toxicity to microorganisms (bacteria, fungi, algae), microbial biomass and dehydrogenase activity. Also, five pure cultures isolated from various sites (two unicellular green algae and three dinitrogen-fixing cyanobacteria) were tested for their ability to metabolise DDT. Viable counts of bacteria and algae declined with increasing DDT contamination while fungal counts, microbial biomass and dehydrogenase activity increased in medium-level contaminated soil (27 mg DDT residues kg(-1) soil). All the tested parameters were greatly inhibited in high-level contaminated soil (34 mg DDT residues kg(-1) soil). Species composition of algae and cyanobacteria was altered in contaminated soils and sensitive species were eliminated in the medium and high contaminated soils suggesting that these organisms could be useful as bioindicators of pollution. Microbial biomass and dehydrogenase activity may not serve as good bioindicators of pollution since these parameters were potentially influenced by the increase in fungal (probably DDT resistant) counts. All the tested algal species metabolised DDT to DDE and DDD; however, transformation to DDD was more significant in the case of dinitrogen-fixing cyanobacteria.

Removal of H2S in down-flow GAC biofiltration using sulfide oxidizing bacteria from concentrated latex wastewater

A biofiltration system with sulfur oxidizing bacteria immobilized on granular activated carbon (GAC) as packing materials had a good potential when used to eliminate H(2)S. The sulfur oxidizing bacteria were stimulated from concentrated latex wastewater with sulfur supplement under aerobic condition. Afterward, it was immobilized on GAC to test the performance of cell-immobilized GAC biofilter. In this study, the effect of inlet H(2)S concentration, H(2)S gas flow rate, air gas flow rate and long-term operation on the H(2)S removal efficiency was investigated. In addition, the comparative performance of sulfide oxidizing bacterium immobilized on GAC (biofilter A) and GAC without cell immobilization (biofilter B) systems was studied. It was found that the efficiency of the H(2)S removal was more than 98% even at high concentrations (200-4000 ppm) and the maximum elimination capacity was about 125 g H(2)S/m(3)of GAC/h in the biofilter A. However, the H(2)S flow rate of 15-35 l/h into both biofilters had little influence on the efficiency of H(2)S removal. Moreover, an air flow rate of 5.86 l/h gave complete removal of H(2)S (100%) in biofilter A. During the long-term operation, the complete H(2)S removal was achieved after 3-days operation in biofilter A and remained stable up to 60-days.

Effects of inoculum to substrate ratio, substrate mix ratio and inoculum source on batch co-digestion of grass and pig manure.

Biochemical methane potential (BMP) assay was conducted at 35 °C to evaluate the effects of inoculum to substrate ratio (ISR) and substrate mix ratio between para-grass and pig manure co-digesting using different inocula. Rubber latex digester (RLD) inoculum showed higher methanogenic activity (41.4 mL CH4/gVS) than pig farm digester (PFD) inoculum (37.3 mL CH4/gVS). However, the maximum methane yields, occurred at the highest para-grass mix ratio (G), were 369.6, 437.6, 465.9 and 442.6 mL CH4/gTSadded for RLD inoculum, versus 332.4, 475.0, 519.5 and 521.9 mL/gTSadded for PFD inoculum at ISR 1, 2, 3, and 4, respectively. HPr, HBu and HVa appeared at higher G, corresponding to substrates higher biodegradability. Response surface indicated that higher ISR and G had a significantly positive impact on methane yield. It suggested the use of higher ISR, i.e. 3 or 4, for BMP assay of these co-substrates. Dominant species of fermentative bacteria in each inoculum was tested by DGGE.

Characterization of exopolymeric substances from selected Rhodopseudomonas palustris strains and their ability to adsorb sodium ions

Removal of Na(+) by binding with exopolymeric substances (EPS) from Rhodopseudomonas palustris TN114 and PP803 was investigated. The moderate negative correlation pairs (rp) between remaining Alcian blue and amount of Na(+) adsorbed on EPS from strains TN114 and PP803 were -0.652 and -0.609. Both strains showed positive relationships between the amounts of EPS produced and bacterial growth. EPS from strain PP803 had a higher efficiency in removing Na(+) than the EPS from strain TN114 based on their EC50 values (1.79 and 1.49 mg/mL for TN114 and PP803, respectively). The principal component from EPS of strain PP803 which was responsible for salt removal was purified and it was identified as a polysaccharide (≈18 kDa) mainly composed of galacturonic acid. Overall results suggested that EPS is a key factor that our strains used to bind Na(+) allowing their survival in high NaCl concentrations.

Production of biomass and extracellular 5-aminolevulinic acid by Rhodopseudomonas palustris KG31 under light and dark conditions using volatile fatty acid.

Kinetic parameters for growth and extracellular 5-aminolevulinic acid (ALA) production of Rhodopseudomonas palustris KG31 under light and dark conditions in a medium containing volatile fatty acids (VFA) as the carbon sources were estimated using a Gompertz model. The lag phase for growth and the maximum specific growth rate under microaerobic-light cultivations were 7.29-12.49 h and 0.038-0.094 h(-1), respectively, whereas under aerobic-dark cultivations, they were 2.03-14.25 h and 0.016-0.022 h(-1), respectively. The lag phase for extracellular ALA production and the maximum specific extracellular ALA production rate under microaerobic-light cultivations (15.72-24.74 h and 0.222-0.299 h(-1), respectively) were better than those obtained under aerobic-dark cultivations (24.57-44.84 h and 0.103-0.215 h(-1), respectively). The biomass and the extracellular ALA yields of 39.66-56.25 gDCW/l/mol C, and 148.47-245.75 μM/mol C, respectively, under microaerobic-light cultivations were higher than of those obtained under aerobic-dark conditions. An enhancement of extracellular ALA production under aerobic-dark conditions revealed that the ALA yield was markedly increased 8-fold (48.36 μM) by the addition of 10mM succinate, 4.5mM glycine, and 15 mM levulinic acid (LA). By controlling dissolved oxygen (DO) and pH values, a maximum extracellular ALA yield of 66.38 μM was found. The degradation rate of ALA in the culture broth was closely related to the pH value.

Influence of Precursors and Inhibitor on the Production of Extracellular 5-Aminolevulinic Acid and Biomass by Rhodopseudomonas palustris KG31

5-Aminolevulinic acid (ALA) and the biomass of photosynthetic bacteria, Rhodopseudomonas palustris KG31, have very high potential for development and exploitation as bioherbicide and biofertilizer respectively. In this work, the effects of two precursors and an inhibitor of aminolevulinic dehydratase (ALAD) added to the VFA culture medium on the production of ALA and biomass were investigated. The experimental runs were carried out according to a Box-Behnken design. The precursors were added to the medium at the beginning of cultivation, while the inhibitor was added after 24 h. Statistical analysis indicated that levulinic acid (LA) has a positive effect on ALA production while glycine has a negative effect on biomass production. In order to enhance both ALA and biomass products, the most suitable medium was VFA medium supplemented with 3.0 mM glycine and 10 mM LA, giving ALA and biomass of 182.91 μM and 3.1 gDCW/l within 54 h.

DDT Resistance and Transformation by Different Microbial Strains Isolated from DDT-Contaminated Soils and Compost Materials

Bioremediation is a potential option to treat 1, 1, 1-trichloro-2, 2-bis (4-chlorophenyl) ethane (DDT) contaminated sites. In areas where suitable microbes are not present, the use of DDT resistant microbial inoculants may be necessary. It is vital that such inoculants do not produce recalcitrant breakdown products e.g. 1, 1-dichloro-2, 2-bis (4-chlorophenyl) ethylene (DDE). Therefore, this work aimed to screen DDT-contaminated soil and compost materials for the presence of DDT-resistant microbes for use as potential inoculants. Four compost amended soils, contaminated with different concentrations of DDT, were used to isolate DDT-resistant microbes in media containing 150 mg l−1 DDT at three temperatures (25, 37 and 55°C). In all soils, bacteria were more sensitive to DDT than actinomycetes and fungi. Bacteria isolated at 55°C from any source were the most DDT sensitive. However DDT-resistant bacterial strains showed more promise in degrading DDT than isolated fungal strains, as 1, 1-dichloro 2, 2-bis (4-chlorophenyl) ethane (DDD) was a major bacterial transformation product, while fungi tended to produce more DDE. Further studies on selected bacterial isolates found that the most promising bacterial strain (Bacillus sp. BHD-4) could remove 51% of DDT from liquid culture after 7 days growth. Of the amount transformed, 6% was found as DDD and 3% as DDE suggesting that further transformation of DDT and its metabolites occurred.

Bio-desulfurization of biogas using acidic biotrickling filter with dissolved oxygen in step feed recirculation.

Triple stage and single stage biotrickling filters (T-BTF and S-BTF) were operated with oxygenated liquid recirculation to enhance bio-desulfurization of biogas. Empty bed retention time (EBRT 100-180 s) and liquid recirculation velocity (q 2.4-7.1 m/h) were applied. H2S removal and sulfuric acid recovery increased with higher EBRT and q. But the highest q at 7.1 m/h induced large amount of liquid through the media, causing a reduction in bed porosity in S-BTF and H2S removal. Equivalent performance of S-BTF and T-BTF was obtained under the lowest loading of 165 gH2S/m(3)/h. In the subsequent continuous operation test, it was found that T-BTF could maintain higher H2S elimination capacity and removal efficiency at 175.6±41.6 gH2S/m(3)/h and 89.0±6.8% versus S-BTF at 159.9±42.8 gH2S/m(3)/h and 80.1±10.2%, respectively. Finally, the relationship between outlet concentration and bed height was modeled. Step feeding of oxygenated liquid recirculation in multiple stages clearly demonstrated an advantage for sulfide oxidation.

Use of Protein Hydrolysate from Yellow Stripe Trevally ( Selaroides leptolepis ) as Microbial Media

The objective of this study was to investigate the potential use of protein hydrolysate from yellow stripe trevally as a nitrogen source for the growth of different microorganisms. Protein hydrolysates from yellow stripe trevally with different degrees of hydrolysis (5, 15 and 25%) prepared using Alcalase (HA) or Flavourzyme (HF) were determined in comparison with commercial Bacto Peptone. For bacteria, Staphylococcus aureus and Escherichia coli, HF with 25% DH (HF25) yielded the highest cell density and specific growth rate (μmax) and the lowest generation time (td) (p < 0.05). For yeasts, Saccharomyces cerevisiae and Candida albicans, Bacto Peptone yielded the higher growth rate than did HA and HF (p < 0.05), whereas no differences in μmax and td were observed for fungus, Aspergillus oryzae (p > 0.05). The pH of culture broth containing HF25 decreased markedly during the first 8 hours of cultivation of S. aureus and E. coli (p < 0.05). This directly lowered the colony size of S. aureus (p < 0.05). However, buffered culture broth containing HF25 rendered the similar growth and colony size of S. aureus (p > 0.05), compared with that containing Bacto Peptone. Scanning electron microscopic study revealed no differences in size and shape of microorganisms cultured in HF25 and Bacto Peptone (p > 0.05).

Microbial succession in a fermenting of wild forest noni (Morinda coreia Ham) fruit plus molasses and its role in producing a liquid fertilizer

The numbers of lactic acid bacteria (LAB) and yeasts that were present during a wild forest noni ( Morinda coreia Ham) fermentation, the changes in its physico-chemical properties and levels of plant nutrients were investigated. LAB increased rapidly during the first 7 days and were the dominant population until after day 21 when the LAB were declining and the yeasts began to dominate. Identification of the LAB and yeasts to species level showed that the dominant LAB throughout was Lactobacillus plantarum while Lactobacillus pentosus was found but only at day 21. Saccharomyces cerevisiae was the most dominant species of yeast throughout but was slowly replaced by Pichia membranifaciens and then Pichia anomala. Rhodotolura mucilaginosa , an aerobic yeast, was only detected at the beginning of the fermentation process. It is suggested that the Pichia spp. were responsible for consuming lactic acid. After 56 days, the values of pH, acetic acid, ethanol and electrical conductivity in the fermented product were 3.66, 3.34 g L -1 , 16.98 g L -1 and 14.47 mS cm -1 , respectively. Increased amounts of plant nutrients were present at day 56 mostly derived from the degradation of plant material. At day 56 the amounts were as follows (in mg L -1 ): N 633, P 1210, K 4356, Ca 693, Mg 536, Mn 7, B 51, Zn 169, and total carbon/total nitrogen ratio (C/N ratio) 18. Based on the seed germination index (GI) of cherry tomato ( Lycopersicon esculentum Mill), the extract diluted 256-fold gave the best GI of 157%.