Removal of soluble COD by a biofilm formed on a membrane in a jet loop type membrane bioreactor

The soluble chemical oxygen demand (COD) removal efficiency through a cake layer (biofilm) deposited on the surfaces of a membrane was investigated as a function of biofilm thickness in a jet loop type membrane bioreactor (JL-MBR). The mechanisms for the removal were investigated based on the microbial characteristics of the biofilm. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was used to identify the microbial community and a Specific oxygen uptake rate (SOUR) analysis was applied to determine the activities of microbial communities in a biofilm. Both the activities and community of microbial communities in the biofilm were similar to those found in a mixed liquor since, in JL-MBR all the substrates, dissolved oxygen, and nutrients are forced to flow through the biofilm, which differs from the biofilms grown on a non-permeable substratum in conventional biofilm process. The removal efficiency of soluble COD in a reactor through the active biofilm increased, reaching a constant value of approximately 92% despite the continuous increase in the thickness of active biofilm with the operation time. This might be attributed to (i) the presence of soluble COD that is not readily biodegraded, (ii) the presence of small and non-biodegradable organic molecules that could easily pass through the biofilm as well as the membrane, and (iii) too short a contact time of soluble solutes with the active microorganisms in the biofilm.     

Microbial community study in a petrochemical industry wastewater treatment system by PCR-DGGE

To improve the efficiency of petrochemical wastewater purification, the relationship between bacterial community structure and pollutants loading/degrading rates in A/O process for petrochemical wastewater treatment was investigated by denaturing gradient gel electrophoresis (DGGE) of the 16S rRNA gene fragments amplified by polymerase chain reaction (PCR). Results show that while the influent COD and NH4+-N concentrations are 425.92-560 mg/L and 64-100 mg/L respectively, the corresponding average concentrations of the effluent are 160 mg/L and 55 mg/L, which are 1.6 and 3.6 times more than the national standards respectively. It demonstrates that the performance of pollutants removal process is inefficient. The analysis of PCR-DGGE profile indicates that the bacterial community structure of the activated sludge in A/O system is species-rich but unstable, and the highest and the lowest similarity coefficients are 36% and 6.25% respectively, which shows that remarkable community structure evolution exists in the system. The variation of bacterial community structure and pollutants loading influences the removal efficiency of pollutants obviously, and relatively stable community structure leads to the stable operational performance of biological wastewater treatment system.     

Application of multi-stage bio-filtration system for sewage treatment and analysis of the microbial community

The conventional fixed-bed biofilm process has disadvantages of easily blocked,high headloss and short operation cycle.For overcoming these disadvantages,a multi-stage biofilm reactor(MSBFR),in which the lightweight floating filter was dominant,was set up and operated.For detail investigation of the system when treating municipal wastewater,the succession characteristic of microbial community was analyzed by polymerase chain reaction(PCR)-Denaturing Gradient Gel Electrophoresis(DGGE)method.The results showed that the process had high efficiency to removal COD,SS and NH4+-N.The concentration of COD,SS and NH4-N in effluent were maintained lower than 40 mg/L,5 mg/L and 2 mg/L even though the concentration of COD,SS and NH4+-N in influent were 232-663 mg/L,105-245 mg/L and 23.7-62.7 mg/L,respectively,and the empty bed retention time was 3 h.Furthermore,biofilm samples taken from the column 2nd in height were analyzed by PCR-DGGE.The result of PCR-DGGE analysis showed that the microbial community had a little change in height and the dominant groups were Paracoccus sp.,Lactobacillus delbrueckii,Pseudomonas sp.and Bacteroidetes bacterium.     

常温CANON反应器内微生物群落结构及生物多样性

为研究基于亚硝化的全程自养脱氮(CANON)工艺中微生物群落结构及种属特征,从常温条件下稳定运行的CANON反应器中采集生物膜样品,并基于聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)技术,分别对总细菌、氨氧化细菌和厌氧氨氧化菌进行群落结构解析.结果表明:反应器中与亚硝化作用有关的功能菌为亚硝化单胞菌属(Nitrosomonas)和亚硝化螺菌属(Nitrosospira),与厌氧氨氧化作用有关的功能菌是Candidatus Brocadia属和CandidatusKuenenia属,未检测到亚硝酸盐氧化细菌,且系统内氨氧化细菌的生物多样性明显高于厌氧氨氧化菌.此外,反应器中还存在其他微生物,如Shewanella 、Pseudomonas 、lgnatzschineria、Dechloromonas以及属于Clostridia、α-Proteobacteria、Bacillales的uncultured bacteium等.     

Effects of combined organic acid treatments during the cutting process on the natural microflora and quality of chicken drumsticks

Reducing the microbial load on broiler chicken carcasses at each stage of poultry meat processing, is highly important for hygienic meat production. This study was conducted to assess the efficacy of various combined organic acid treatments during the cutting process on the microbial decontamination of chicken drumsticks. Changes in naturally occurring microflora before and after treatment were analyzed through microbiological counting and polymerase chain reaction–denaturing gradient gel electrophoresis (PCR-DGGE). Results revealed that the most effective treatments obtained through the combination of orthogonal design and sensory evaluation were as follows: 0.5% lactic acid (w/v), 1% citric acid (w/v), and spray-washing for 30 s. Microbiological counting results and PCR-DGGE analysis indicated that the microbial load on the chicken drumsticks decreased significantly after the treatment was administered. The treatment did not affect the physicochemical properties and sensory attributes of the quick-frozen chicken drumsticks during storage. Therefore, the proposed technique could be used to improve the microbial quality of chicken drumsticks. The technique could also be employed in poultry meat production chains.     

Volatile compounds and bacterial community dynamics of chestnut-flour-based sourdoughs

The aims of this study were the monitoring of the microbial dynamics by means of a polyphasic approach based on conventional isolation techniques and PCR-DGGE-based methods in different chestnut-based sourdoughs and the evaluation of the impact of fermentation on volatile organic compounds formation during sourdoughs ripening. Members of the Lactobacillus plantarum group and Pediococcus pentosaceous dominated the sourdough ecosystems. Nevertheless, RAPD-PCR allowed recording a relevant genotypic biodiversity among strains coming from gluten-free flour combinations. Volatile compounds were characterised by GC/MS. A total of 59 volatile compounds were identified, mainly alcohols, esters, acids, aldehydes and ketones. Principal component analysis of samples at the beginning and at the end of ripening offered a good separation of the samples and highlighted the effect of fermentation on the sensorial profile.     

Hydrogen production from acid and enzymatic oat straw hydrolysates in an anaerobic sequencing batch reactor: Performance and microbial population analysis

Feasibility of hydrogen production from acid and enzymatic oat straw hydrolysates was evaluated in an anaerobic sequencing batch reactor at 35 °C and constant substrate concentration (5 g chemical oxygen demand/L). In a first experiment, hydrogen production was replaced by methane production. Selective pressures applied in a second experiment successfully prevented methane production. During this experiment, initial feeding with glucose/xylose, as model substrates, promoted biomass granulation. Also, the highest hydrogen molar yield (HMY, 2 mol H₂/mol sugar consumed) and hydrogen production rate (HPR, 278 mL H₂/L-h) were obtained with these model substrates. Gradual substitution of glucose/xylose by acid hydrolysate led to disaggregation of granules and lower HPR and HMY. When the model substrates were completely substituted by enzymatic hydrolysate, the HMY and HPR were 0.81 mol H₂/mol sugar consumed and 29.6 mL H₂/L-h, respectively. Molecular analysis revealed a low bacterial diversity in the stages with high hydrogen production and vice versa. Furthermore, Clostridium pasteurianum was identified as the most abundant species in stages with a high hydrogen production. Despite that feasibility of hydrogen production from hydrolysates was demonstrated, lower performance from hydrolysates than from model substrates was obtained.     

茶多酚对apoE-/-小鼠脂类代谢和肠道双歧杆菌的影响

研究茶多酚对小鼠脂类代谢和结肠双歧杆菌的影响,探讨茶多酚采食与脂类代谢和肠道双歧杆菌之间的关系。ApoE-/-小鼠以高脂饲料饲养并在饮水中添加1.6g/L茶多酚,8周后用变性梯度凝胶电泳(DGGE)分析肠道双歧杆菌多样性。结果表明,高脂饮食对照组(HF)和茶多酚组(T)肠道双歧杆菌多样性有显著差异;16周后,T组血清中TC、LDL-C含量分别为19.8,16.1mmol/L,显著低于HF组的36.4,28.4mmol/L(P<0.05)。说明茶多酚采食对apoE-/-小鼠肠道双歧杆菌菌群多样性和脂类代谢均有显著的影响。