Effects of elevated temperature on bacterial community structure and function in bioreactors treating a synthetic wastewater

The impact of elevated temperature on bacterial community structure and function during aerobic biological wastewater treatment was investigated. Continuous cultures, fed a complex growth medium containing gelatin and α-lactose as the principal carbon and energy sources, supported mixed bacterial consortia at temperatures ranging from 25–65°C. These temperature- and substrate-acclimated organisms were then used as inocula for batch growth experiments in which the kinetics of microbial growth and substrate utilization, efficiency of substrate removal, and mechanism of substrate removal were compared as functions of temperature. Bacterial community analysis by denaturing gradient gel electrophoresis (DGGE) revealed that distinct bacterial consortia were supported at each temperature. The efficiency of substrate removal declined at elevated temperatures. Maximum specific growth rates and the growth yield increased with temperature from 25–45°C, but then decreased with further elevations in temperature. Thus, maximum specific substrate utilization rates did not vary significantly over the 40°C temperature range (0.64 ± 0.04 mg COD mg⁻¹ dry cell mass h⁻¹). A comparison of the degradation of the protein and carbohydrate portions of the feed medium revealed a lag in α-lactose uptake at 55°C, whereas both components were utilized simultaneously at 25°C. Journal of Industrial Microbiology & Biotechnology (2000) 24, 140–145. Received 09 August 1999/ Accepted in revised form 12 November 1999     

Bioaugmentation with a novel alkali-tolerant Pseudomonas strain for alkaline phenol wastewater treatment in sequencing batch reactor

A novel alkali-tolerant strain JY-2, which could utilize phenol as sole source of carbon and energy, was isolated from activated sludge. It was identified as Pseudomonas sp. by 16S rDNA sequencing analysis. The appropriate conditions for strain growth and phenol biodegradation were as follows: pH 8.0–10.0 and temperature 23–30°C. With initial phenol concentrations of 225, 400, 550 and 750 mg/l, the degradation efficiencies were 94.9, 93.3, 89.3 and 48.2% within 40 h at pH 10.0 and 30°C, respectively. The alkaline phenol-containing wastewater treatment augmented with strain JY-2 in sequencing batch reactor (SBR) system was investigated, which suggested that the bioaugmented (BA) system exhibited the better performance for adjusting high pH to neutral value than the non-bioaugmented (non-BA) one. Also, the BA system showed strong abilities for phenol degradation and maintaining good sedimentation coefficient (SV₃₀). The microbial community dynamics of both sequencing batch reactor (SBR) systems were analyzed by Denaturing Gradient Gel Electrophoresis (DGGE) technique, which showed substantial changes between the two systems. This study suggests that it is feasible to treat alkaline phenol-containing wastewater augmented with strain JY-2.     

Degradation of RNA during the autolysis of Saccharomyces cerevisiae produces predominantly ribonucleotides

Autolytic degradation of yeast RNA occurs in many foods and beverages and can impact on the sensory quality of the product, but the resulting complex mixture of nucleotides, nucleosides and nucleobases has not been properly characterised. In this study, yeast autolysis was induced by incubating cell suspensions of Saccharomyces cerevisiae at 30–60 °C (pH 7.0), and at pH 4.0–7.0 (40 °C) for 10–14 days, and the RNA degradation products formed during the process were determined by reversed-phase HPLC. Up to 95% of cell RNA was degraded, with consequent leakage into the extracellular environment of mainly 3′-, 5′- and 2′-ribonucleotides, and lesser amounts of polynucleotides, ribonucleosides and nucleobases. The rate of RNA degradation and the composition of the breakdown products varied with temperature and pH. RNA degradation was fastest at 50 °C (pH 7.0). Autolysis at lower temperatures (30 °C and 40 °C) and at pH 5.0 and 6.0 favoured the formation of 3′-nucleotides, whereas autolysis at 40 °C and 50 °C (pH 7.0) favoured 5′- and 2′-nucleotides. The best conditions for the formation of the two flavour-enhancing nucleotides, 5′-AMP and 5′-GMP, were 50 °C (pH 7.0) and pH 4.0 (40 °C), respectively.     

Degradation of DNA during the autolysis of<Emphasis Type="Italic"> Saccharomyces cerevisiae</Emphasis>

The autolysis of yeast cells has practical implications in the production of fermented foods and beverages and flavourants for food processing. Protein and RNA degradation during yeast autolysis are well described but the fate of DNA is unclear. Yeast cells (Saccharomyces cerevisiae) were autolysed by incubating suspensions at 30–60°C (pH 7.0), and at pH 4.0–7.0 (40°C) for 10–14 days. Up to 55% of total DNA was degraded, with consequent leakage into the extracellular environment of mainly 3′- and 5′-deoxyribonucleotides, and lesser amounts of polynucleotides. The rate and extent of DNA degradation, composition of the DNA degradation products and DNase activity were affected by temperature and pH. The highest amount of DNA degradation occurred at 40°C and pH 7.0, where the highest DNase activity was recorded. DNase activity was lowest at 60°C and pH 4.0, where the proportion of polynucleotides in the degradation products was higher. Electronic Publication     

Condition stabilization for <Emphasis Type="Italic">Aspergillus niger</Emphasis> FCBP-198 and its hyperactive mutants to yield high titres of α-amylase

A number of substrates were tested for the cultivation of microorganisms to produce a host of enzymes. The effect of different substrates (wheat and rice straw, sugar cane waste, wood waste), incubation temperatures (20–40°C), initial pH levels (3.5–9.0), incubation periods (0–72 hours) and nitrogen sources (ammonium sulfate, urea, peptone, yeast extract, sodium nitrate) on growth and α-amylase activity was studied for the native and mutant strains. Maximum enzyme activity was observed at 1.5% wheat straw for Aspergillus niger FCBP-198 and An-Ch-4.7 and at 2% wheat straw for An-UV-5.6, with sodium nitrate as a principle nitrogen source. The optimum temperature for maximum enzyme activity was 30°C for the parental strain, while An-UV-5.6 and An-Ch-4.7 thrived well at 32.5°C. The best conditions of pH and incubation duration were 4.5 and 48 hours, respectively, for all the strains. Mass production under preoptimized growth conditions demonstrated the suitability of wheat straw for swift mycelial colonization and viability.     

Bioaugmentation of Bromoamine Acid Degradation with Sphingomonas xenophaga QYY and DNA Fingerprint Analysis of Augmented Systems

One high-effective bromoamine acid (1-amino-4-bromoanthraquinone-2-sulfonic acid, BAA) degrading strain was isolated previously with the ability to use BAA as sole source of carbon and nitrogen. It was identified as Sphingomonas xenophaga QYY by 16S rDNA sequence analysis and physio-biochemical tests. In this study, bioaugmentation of BAA degradation with suspended and immobilized cells of strain QYY was investigated. The optimal degradation conditions were as follows: temperature 30 °C, pH 6.0–7.0, 150 rev min⁻¹ and the immobilized cells maintained degradation activity to BAA after 60 days storage at 4 °C. The structure of BAA was evidently changed according to the analysis of total organic carbon removal of BAA (about 50%) and the UV–VIS spectra changes during the biodegradation. Bioaugmented systems exhibited stronger abilities degrading BAA than the non-bioaugmented control ones. And microbial community dynamics of augmented systems was revealed by amplified ribosomal DNA restriction analysis (ARDRA), a modern DNA fingerprint technique. The results indicated that the microbial community dynamics was substantially changed throughout the augmentation process. This study suggests that it is feasible and potentially useful to enhance BAA degradation using bioaugmentation with the immobilized cells of BAA-degrading bacterium.     

Production of thermotolerant and alkalotolerant cellulolytic enzymes by isolated <Emphasis Type="Italic">Nocardiopsis</Emphasis> sp. KNU

A novel cellulolytic bacterium was isolated from the forest soil of KNU University campus. Through 16S rRNA sequence matching and morphological observation it was identified as Nocardiopsis sp. KNU. This strain can utilize a broad range of cellulosic substrates including: carboxymethyl cellulose (CMC), avicel, xylan, cellobiose, filter paper and rice straw by producing a large amount of thermoalkalotolerant endoglucanase, exoglucanase, xylanase and glucoamylase. Optimal culture conditions (Dubos medium, 37°C, pH 6.5 and static condition) for the maximal production of the cellulolytic enzymes were determined. The activity of cellulolytic and hemicelluloytic enzymes produced by this strain was mainly present extracellularly and the enzyme production was dependent on the cellulosic substrates used for the growth. Effect of physicochemical conditions and metal additives on the cellulolytic enzymes production were systematically investigated. The cellulases produced by Nocardiopsis sp. KNU have an optimal temperature of 40°C and pH of 5.0. These cellulases also have high thermotolerance as evidenced by retaining 55–70% activity at 80°C and pH of 5.0 and alkalotolerance by retaining >55% of the activity at pH 10 and 40°C after 1 h. The efficiency of fermentative conversion of the hydrolyzed rice straw by Saccharomyces cerevisiae (KCTC-7296) resulted in 64% of theoretical ethanol yield.     

Biooxidation of a gold-containing sulfide concentrate in relation to changes in physical and chemical conditions

The growth of a microbial community and the oxidation of iron- and sulfur-containing substrates in batch culture during the leaching/oxidation of the flotation concentrate of refractory gold-arsenic sulfide ore were optimized with respect to the following medium parameters: temperature, pH, and requirement in organic substances. It was revealed that the optimum mode is (i) to maintain the pH at 1.6–1.7 and the temperature at 34–35 and 38°C and (ii) to add Corg in the form of yeast extract (0.02%). Mutually beneficial or competitive relationships among groups of microorganisms of the community were established, depending on the cultivation conditions.     

Identification and characterization of fermentation inhibitors formed during hydrothermal treatment and following SSF of wheat straw

A pilot plant for hydrothermal treatment of wheat straw was compared in reactor systems of two steps (first, 80°C; second, 190–205°C) and of three steps (first, 80°C; second, 170–180°C; third, 195°C). Fermentation (SSF) with Sacharomyces cerevisiae of the pretreated fibers and hydrolysate from the two-step system gave higher ethanol yield (64–75%) than that obtained from the three-step system (61–65%), due to higher enzymatic cellulose convertibility. At the optimal conditions (two steps, 195°C for 6 min), 69% of available C6-sugar could be fermented into ethanol with a high hemicellulose recovery (65%). The concentration of furfural obtained during the pretreatment process increased versus temperature from 50 mg/l at 190°C to 1,200 mg/l at 205°C as a result of xylose degradation. S. cerevisiae detoxified the hydrolysates by degradation of several toxic compounds such as 90–99% furfural and 80–100% phenolic aldehydes, which extended the lag phase to 5 h. Acetic acid concentration increased by 0.2–1 g/l during enzymatic hydrolysis and 0–3.4 g/l during fermentation due to hydrolysis of acetyl groups and minor xylose degradation. Formic acid concentration increased by 0.5–1.5 g/l probably due to degradation of furfural. Phenolic aldehydes were oxidized to the corresponding acids during fermentation reducing the inhibition level.     

Metabolic resistance of a psychrotolerant VFA-oxidizing microbial community from an anaerobic bioreactor to changes in the cultivation temperature

A psychrotolerant microbial consortium from a low-temperature anaerobic EGSB bioreactor was grown separately on acetate, propionate, butyrate, and H₂/CO₂ at 30 and 10°C in glass flasks. In the course of the experiments, the cultivation temperature was changed at different time intervals. The initial rates of substrate utilization were higher at 30 than at 10°C. However, the microbial consortium was found to be well adapted to low temperatures; when grown at 10°C for 1.5–5 months, the rates of butyrate, propionate, and H₂/CO₂ utilization increased steadily. When grown at 30°C for 1.5–2.5 months, this consortium retained its ability to degrade VFA and H₂/CO₂ at 10°C. However, after long-term (150 days) cultivation at 10°C, its ability to utilize the substrates at 30°C decreased. In the consortium grown in the acetate-containing medium, a Methanosaeta-like methanogen was predominant; in media with propionate and butyrate, besides VFA-degrading bacteria, acetoclastic Methanosaeta-like and hydrogenotrophic Methanospirillum-like methanogenic archaea prevailed. A Methanospirillum-like strain predominated in the H₂/CO₂-containing medium. The Methanospirillum strain of this microbial community was presumably psychrotolerant. A method based on changes in the cultivation temperature is of practical interest and can be used to start up new bioreactors.     

一株低温玉米秸秆降解真菌的筛选、鉴定及降解特性

【背景】在我国北方地区玉米秸秆还田时期地温低、秸秆降解慢,如何加速玉米秸秆低温腐解成为研究热点。【目的】从冷凉地区土壤中筛选具有高效降解纤维素能力的低温菌株,为秸秆的有效利用奠定基础。【方法】在低温培养条件下,采用稀释涂布平板法、羧甲基纤维素钠(sodium carboxymethyl cellulose,CMC-Na)水解圈测定法、胞外酶活测定法、秸秆失重法进行低温秸秆降解菌株的初筛、复筛和秸秆降解性能的测定;根据菌株形态学特征及ITSrDNA序列分析对筛选菌株进行鉴定;利用3,5-二硝基水杨酸(3,5-dinitrosalicylic acid,DNS)法和秸秆失重法对菌株在不同接种量、培养基初始pH、温度情况下的纤维素酶活力和玉米秸秆降解能力进行研究。【结果】以16°C为筛选温度,获得一株在刚果红-羧甲基纤维素钠平板上D/d值为2.17、CMC酶活力为703 U/mL的高产纤维素酶低温真菌SDF-25;该菌株在4°C可以生长,10-16°C为最适生长温度,37°C条件下仍能生长;综合菌株的形态学和分子生物学测定结果,菌株SDF-25为草酸青霉菌(Penicillium oxalicum);该菌株最佳产纤维素酶的培养条件为接种量2%、初始pH为7.0、培养温度为10°C,在该培养条件下菌株SDF-25的CMC酶活为993.3 U/mL。失重法测定接种SDF-25于10°C培养15 d时秸秆降解率为39.5%,16°C时为44.9%。【结论】草酸青霉菌SDF-25可在低温条件下生长并具有较强的纤维素酶生产能力,在秸秆还田方面具有良好的应用前景。     

Specific characteristics of the strains isolated from a thermoacidophilic microbial community oxidizing antimony sulfide ore

Investigation of the phenotypic properties of three mixotrophic bacteria, strains Sb-K, Sb-F, and Sb-S, isolated from an aboriginal thermoacidophilic microbial community participating in biooxidation of ore with high antimony content (26%) and ore concentrates from the Olympiadinskoe deposit under semicontinuous cultivation conditions at 46 ± 1°C, revealed the differentiating characteristics of these strains. The isolated cultures grew lithotrophically through different numbers of transfers: strains Sb-F and Sb-K grew through seven and eight transfers, respectively, and strain Sb-S grew through two or three transfers. Strains Sb-K and Sb-S utilized a wide range of organic substrates for active organotrophic growth during nine or ten transfers, while strain Sb-F was less tolerant to organic compounds. Strain Sb-K grew on a medium with the ore and sulfide ore concentrates in the pH range of 1.0–3.0. Growth of strains Sb-F and Sb-S occurred in the pH ranges of 1.0–2.5 and 1.5–5.5 on media with Fe²⁺ and S⁰, respectively.. The optimal initial pH values of the media, corresponding to the maximum specific growth rates, were 1.6–1.7, 1.9, and 2.0–3.0 for strains Sb-K, Sb-F, and Sb-S, respectively. All three strains were able to grow within a broad temperature range, 20–65°C, with an optimum at 46°C (Sb-K), 40–46°C (Sb-F), and 48–50°C (Sb-S). According to the results of DNA-DNA hybridization and phylogenetic analysis, as well as their phenotypic characteristics, the isolates can be classified as novel strains of species of the genus Sulfobacillus. Strains Sb-K, Sb-F, and Sb-S, isolated as predominant cultures on the media with sulfide compounds, iron, or sulfur, respectively, were affiliated to the species S. thermotolerans, S. sibiricus, and S. thermosulfidooxidans.     

Cell viability and protein turnover in nongrowingBacillus megaterium at sporulation suppressing temperature

InBacillus megaterium, a temperature that suppresses sporulation (43°C) only slightly exceeds both the optimum growth temperature and the temperature still permitting sporulation (40–41°C). Here we show that, when cells grown at 35°C and transferred to a sporulation medium, were subjected to shifts between 35°C and the sporulation suppressing temperature (SST, 43°C), their development and proteolytic activities were deeply affected. During the reversible sporulation phase that took place at 35°C for 2–3 h (T₂–T₃), the cells developed forespores and their protein turnover was characterized by degradation of short-lived proteins and proteins made accessible to the proteolytic attack because of starvation. During the following irreversible sporulation phase refractile heat-resistant spores appeared at T₄–T₅. Protein turnover rate increased again after T₂ and up to T₈ 60–70% prelabelled proteins were degraded. The SST suppressed sporulation at its beginning; at T₃ no asymmetric septa were observed and the amount of heat-resistant spores at T₈ was by 4–5 orders lower than at 35°C. However, the cells remained viable and were able to sporulate when transferred to a lower temperature. Protein degradation was increased up to T₃ but then its velocity sharply dropped and the amount of degraded protein at T₈ corresponded to slightly more than one-half of that found at 35°C. The cytoplasmic proteolytic activity was enhanced but the activity in the membrane fraction was decreased. When a temperature shift to SST was applied at the beginning of the irreversible sporulation phase (T_2.5), the sporulation process was impaired. A portion of forespores lyzed, the others were able to complete their development but most spores were not heat-resistant and their coats showed defects. Protein degradation increased again because an effective proteolytic system was developed during the reversible sporulation phase but the amount of degraded protein was slightly lower than at 35°C. A later (T₄) shift to SST had no effect on the sporulation process.     

Rice straw fermentation using lactic acid bacteria

To efficiently utilize rice straw and lessen its disposal problem on the environment, a lactic acid bacteria community, SFC-2 was developed from natural fermentation products of rice straw by continuous enrichment with the MRS-S broth (MRS broth with sucrose), and used to accelerate the fermentation of air-dried straws. The SFC-2 could rapidly lower the pH of the broth and produce high levels of lactic acid. Using a combination of plate isolation, denaturing gradient gel electrophoresis (DGGE) and 16S rDNA sequencing, the microbial composition of the SFC-2 was classified into Lactobacillus, mainly comprised of L. fermentum, L. plantarum and L. paracacei. An evaluation of the fermentation effect of SFC-2 on rice straw showed that it lowered the pH and significantly (P<0.05) increased lactic acid concentration in the straw. Further analysis with DGGE indicated that L. plantarum, L. fermentum and L. paracasei were the dominant species during fermentation.     

Thermolabile xylanase of the Antarctic yeast Cryptococcus adeliae: production and properties

Xylanase production by the Antarctic psychrophilic yeast Cryptococcus adeliae was increased 4.3 fold by optimizing the culture medium composition using statistical designs. The optimized medium containing 24.2 g l⁻¹ xylan and 10.2 g l⁻¹ yeast extract and having an initial pH of 7.5 yielded xylanase activity at 400 nkat (nanokatal) ml⁻¹ after 168-h shake culture at 4°C. In addition, very little endoglucanase, β-mannanase, β-xylosidase, β-glucosidase, α-l-arabinofuranosidase, and no filter paper cellulase activities were detected. Among 12 carbon sources tested, maximum xylanase activity was induced by xylan, followed by lignocelluloses such as steamed wheat straw and alkali-treated bagasse. The level of enzyme activity produced on other carbon sources appeared to be constitutive. Among the complex organic nitrogen sources tested, the xylanase activity was most enhanced by yeast extract, followed by soymeal, Pharmamedia (cotton seed protein), and Alburex (potato protein). A batch culture at 10°C in a 5-l fermenter (3.5-1 working volume) using the optimized medium gave 385 nkat at 111 h of cultivation. The crude xylanase showed optimal activity at pH 5.0–5.5 and good stability at pH 4–9 (21 h at 4°C). Although the enzyme was maximally active at 45°–50°C, it appeared very thermolabile, showing a half-life of 78 min at 35°C. At 40°–50°C, it lost 71%–95% activity within 5 min. This is the first report on the production as well as on the properties of thermolabile xylanase produced by an Antarctic yeast. Received: December 10, 1999 / Accepted: March 23, 2000     

Synergistic biodegradation of pentachlorophenol by <Emphasis Type="Italic">Bacillus cereus</Emphasis> (DQ002384), <Emphasis Type="Italic">Serratia marcescens</Emphasis> (AY927692) and <Emphasis Type="Italic">Serratia marcescens</Emphasis> (DQ002385)

The consortium of Bacillus cereus (DQ002384), Serratia marcescens (AY927692) and Serratia marcescens (DQ002385) were used for pentachlorophenol (PCP) degradation. The consortia showed better overall removal efficiencies than single strains by utilization of PCP as a carbon and energy source confirmed by pH dependent dye indicator bromocresol purple (BCP) in mineral salt media (MSM). Mixed culture was found to degrade up to 93% of PCP (300 mg/l) as compared to single strains (62.75–90.33%), at optimized conditions (30 ± 1°C, pH 7 ± 0.2, 120 rpm) at 168 h incubation. PCP degradation was also recorded at 20°C (62.75%) and 37°C (83.33%); pH 6 (70%) and pH 9 (75.16%); 50 rpm (73.33%) and 200 rpm (91.63%). The simultaneous release of chloride ion up to 90.8 mg/l emphasized the bacterial dechlorination in the medium. GC–MS analysis revealed the formation of low molecular weight compound, i.e., 6-chlorohydroxyquinol, 2,3,4,6-tetrachlorophenol and tetrachlorohydroquinone, from degraded sample as compared to control.     

Nicotine degradation by two novel bacterial isolates of <Emphasis Type="Italic">Acinetobacter</Emphasis> sp. TW and <Emphasis Type="Italic">Sphingomonas</Emphasis> sp. TY and their responses in the presence of neonicotinoid insecticides

Two novel nicotine-degrading bacterial strains were isolated from tobacco waste and identified as Acinetobacter sp. TW and Sphingomonas sp. TY based on morphology, physiological and biochemical tests, Biolog analysis and 16S rDNA sequencing. The 16S rDNA sequences have been deposited in GenBank under the accession numbers FJ753401 for TW and FJ754274 for TY. The best culture conditions for nicotine degradation were 25–37°C and pH 7.0–8.0 for strain TW and 25–30°C and pH 6.0–7.0 for strain TY. Under the best conditions, the cell growth and nicotine-degradation kinetics of the two isolates were assessed, and 1.0 g/l nicotine was completely degraded within 12 and 18 h for TW and TY, respectively. Moreover, the presence of four widely-used commercial neonicotinoid insecticides in the medium had no effects on nicotine degradation by TW; among the four tested neonicotinoids, only thiamethoxam significantly delayed nicotine degradation by TY. TW and TY were also able to degrade selected neonicotinoids. This is the first report of nicotine degradation by Acinetobacter sp. and Sphingomonas sp. This study showed that these two newly isolated bacteria may be suitable for the disposal of tobacco waste and the reduction of nicotine in tobacco leaves.     

Microbial degradation of cyanide and thiocyanate

The role played by a bacterial community composed ofPseudomonas putida, strain 21;Pseudomonas stutzeri, strain 18; andPseudomonas sp., strain 5, and by physical and chemical factors in the degradation of CN⁻ and SCN⁻ was studied. It was shown that the degradation of CN⁻ is determined both by the action of bacteria and by abiotic physical and chemical factors (pH, O₂, temperature, the medium agitation rate, etc.). The contribution of chemical degradation was found to increase drastically at pH below 9.0; when air was blown through the medium (irrespective of the pH value); under active agitation of the medium; and when the medium surface interfacing air was increased. Even at elevated pH values (9.0-9.2), suboptimal for bacterial growth, the microbial degradation could account for at most 20–25 mg/1 of CN⁻, regardless of its initial concentration. When CN⁻ and SCN⁻ were concurrently present in the medium, the former compound was the first to be degraded by microorganisms. The rate of bacterial degradation of SCN⁻ under continuous cultivation in a chain of reactors was found to depend on its concentration, the medium flow rate, agitation rate, and the pattern of carbon source supply and could exceed 1 g/(l day). CN⁻ and SCN⁻ are utilized by bacteria solely as nitrogen sources. The mechanism of CN⁻ and SCN⁻ degradation by the microbial community is discussed. Deceased.     

A study of the efficiency of edible oils degraded in alkaline conditions by <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> SS-219 and <Emphasis Type="Italic">Acinetobacter</Emphasis> sp. SS-192 bacteria isolated from Japanese soil

High lipid concentration contained in wastewater inhibits the activity of microorganisms in biological wastewater treatment systems such as activated sludge and methane fermentation. To reduce the inhibitory effects, microorganisms capable of efficiently degrading edible oils were screened from various environmental sources. From Japanese soil, we isolated 2 bacteria strains with high degradation abilities at an alkaline pH without consumption of biological oxygen demand (BOD) constituents. Acinetobacter sp. strain SS-192 and Pseudomonas aeruginosa strain SS-219 degraded 77.5 ± 0.6% and 89.5 ± 1.5%, respectively, of 3,000 ppm of mixed oil consisting of salad oil/lard/beef tallow (1/1/1, w/w/w) at 37°C and pH 9.0 in 24 h. Efficient degradation by the two strains occurred at pH 8–9 and 25–40°C. Strain SS-219 degraded lipids even at pH 3. The degradation rate of 3,000 ppm of salad oil, lard, and beef tallow by strain SS-192 was 79.9 ± 2.6%, 63.6 ± 1.9%, and 70.1 ± 1.2%, respectively, during a 24-h cultivation. The degradation rate of 3,000 ppm of salad oil, lard, and beef tallow by strain SS-219 was 82.3 ± 2.1%, 71.9 ± 2.2%, and 71.0 ± 1.1%, respectively, during a 24-h cultivation. After mixed oil degradation by both strains, the BOD value of the cell culture increased from 2,100 ppm to 3,200–4,000 ppm. The fact that neither strain utilizes BOD ingredients will be beneficial to pretreatment of methane fermentation systems such as upflow anaerobic sludge blanket reactors. In addition, the growth of usual heterotrophic microorganisms utilizing soluble BOD can be suppressed under alkaline pH.     

Effects of wetland degradation on bacterial community in the Zoige Wetland of Qinghai-Tibetan Plateau (China)

Wetland degradation makes significant impacts on soil, and bacterial communities in soil are likely to respond to these impacts. The purpose of this study was to investigate the impacts of soil property, soil type and soil depth on bacterial community in different stages of soil degradation in the Zoige Wetland. Microbial biomass carbon was estimated from chloroform fumigation-extraction. Bacterial communities were evaluated by cluster and principal component analysis of DGGE banding patterns and sequencing of partial 16S rDNA PCR amplicons. Experimental results showed that microbial biomass carbon decreased with the soil types (Peat soil > Swamp soil > Meadow soil > Sandy soil) and declined with soil depths (0–20 > 20–40 > 40–60 cm). Bacterial community was affected by soil type more primarily than by soil depth. In addition, the microbial biomass carbon was strongly correlated with soil water content, soil organic carbon and total nitrogen. Sequence analysis of DGGE bands indicated that bacterial phyla of α-Proteobacteria, γ-Proteobacteria, Bacteroidetes, Flavobacterium and Unidentified bacterium predominantly existed in the soil. All these results suggest that specific changes in soil property, soil type and soil depth affected soil bacterial community both quantitatively and qualitatively.