Comparative analysis of hydrogen-producing bacteria and its immobilized cells for characteristics of hydrogen production

A strain of hydrogen producing bacteria was immobilized by polyvinyl alcohol-boric acid method, with the addition of a small amount of calcium alginate. The immobilized cells were insensitive to the presence of traces of O2. Moreover, the immobilized cells increased both the evolution rate and the yield of hydrogen production. Batch experiments with a medium containing 10 g/L glucose demonstrated the yields of hydrogen production by the immobilized and free cells were 2.14 mol/mol glucose and 1.69 mol/mol glucose, respectively. In continuous cultures at medium retention time of 2.0 h, the yield and the evolution rate of hydrogen production by the immobilized cells were 2.31 mol/mol glucose and 1 435.4 ml/（L·h） respectively. However, at medium retention time of 6.0 h, the yield and the evolution rate of hydrogen production by free cells were only 1.75 mol/mol glucose and 362.9 ml/（L·h）, respectively.

Identification of the Electricity-Producing Bacteria in Wastewater for Microbial Fuel Cells （MFCs）

A microbial fuel cell （MFC） is a device that converts chemical energy to electrical energy during substrate oxidation by microorganisms. The characterization and identification of these microbial communities will allow better control of this electricity generation with simultaneous removal of carbon and nitrogen. This study aims to investigate the role of natural bacteria in electricity generation by studying three different sources of wastewater： the raw wastewater （RW）, wastewater from an aeration tank （AEW） and returned activated sludge （RAS） from an activated sludge treatment plant. The result showed that after the MFC treatment, the number of bacterial strains was reduced from twenty strains to eight strains. Microscopic observation further showed that fifteen isolate before the treatment were gram-positive, and five were gram-negative whereas all isolates after the treatment were gram-positive rods or cocci The four strains isolated from the RAS inoculums, β-Comamonas sp., γ-Enterobacter sp., Bacillus cereus sp. and Clostridium sp. produced the highest power density of 67.57 mW/m^2 which made them potential candidates for electrochemically active bacteria in MFCs. However, the level of chemical oxygen demand （COD） removal was 20% and the total kjeldahl nitrogen （TKN） removal was 66.7%. Key words：

POLY (β-HYDROXYALKANOATES): NATURAL BIOCOMPATIBLE AND BIODEGRADABLE POLYESTERS PRODUCED BY BACTERIA

A wide variety of different types of microorganisms are known to produce intracellular energy and carbon storage products, which have been generally described as being poly (β-hydroxybutyrate), PHB, but which are, more often than not, copolymers containing different alkyl groups at the β-position. Hence, PHB belongs to the family ofpoly (β-hydroxyalkanoastes), PHA, all of which are usually formed as intracellular inclusions in bacteria under unbalanced growth conditions. Recently, it became of industrial interest to evaluate these PHA polyesters as natural biodegradable and biocompatible plastics for a wide range of possible applications, such as surgical sutures or packaging containers. For industrial applications, the controlled incorporation of repeating units with different chain lengths into a series of copolymers is desirable in order to produce polyesters with a range of material properties because physical and chemical characteristics depend strongly on the polymer composition. Such 'tailor-made' copolymers can be produced under controlled growth conditions in that, if a defined mixture of substrates for a certain type of microorganisms is supplied, a well defined and reproducible copolymer is formed.

Microbial diversity and functionally distinct groups in produced water from the Daqing Oilfield,China

The microbial community structure and functionally distinct groups in three kinds of produced water samples from the shallow,mesothermic and low-salinity Daqing oil reservoir were systematically evaluated using both culture-dependent and culture-independent methods.Sequence analysis of the 16S rRNA genes indicated that the bacterial library was dominated by Acinetobacter and Arcobacter and the archaeal community was dominated by Methanosaeta and Methanolinea.Two isolated methanogens were closely related with Methanothermobacter thermautotrophicus and Methanoculleus receptaculi.The fermentative bacteria were identified as Pseudomonas,Haloanaerobium,Alcalibacter,Arcobacter,and Pannonibacter.The predominant nitrate-reducing bacteria fell within the genus Pseudomonas.The dominant members of the cultured hydrocarbon-oxidizing bacteria were phylogenetically associated with Micrococcus,Pseudomonas,and Bacillus.Enrichments of biosurfactants and biopolymer producing groups mainly yielded Pseudomonas,Bacillus,and Acenitobacter-related members.The functional groups related to polymer degradation were also affiliated with Pseudomonas and Bacillus.Results from this study provide the fresh insight into the diversity of microbial communities in Daqing petroleum reservoirs.The vast pool of functional strains retrieved in this study was presumed to include the promising strains that could be applied in microbial-enhanced oil recovery in future.

四川泡菜产生物胺细菌的筛选及产胺能力验证

以四川工业泡菜和家庭泡菜为研究对象,分析其一般理化性质、微生物数量及生物胺含量,并对产生物胺细菌进行筛选及产胺能力验证。结果表明,四川工业泡菜的盐度较高,为(11.15±0.11) mg/kg,菌落总数及乳酸菌总数较低,家庭泡菜的pH较低,总酸含量较高,分别为(3.55±0.04),(1.30±0) g/100 g。腐胺、尸胺、组胺、酪胺为四川泡菜主要的生物胺,含量均超过100 mg/kg,且在四川工业泡菜中,尸胺含量高达(349.43±13.23) mg/kg。从四川泡菜中筛选出11株产生物胺的细菌,经鉴定分别为解鸟氨酸拉乌尔菌( Raoultella ornithinolytica)、弗氏柠檬酸杆菌(Citrobacter freundii)、特基拉芽孢杆菌(Bacillus tequilensis)、阿耶波多氏芽孢杆菌(Bacillus aryabhattai),其中R.ornithinolytica 含有赖氨酸脱羧酶cacd基因和组氨酸脱羧酶hdc基因,且回接培养基验证了其具有尸胺和组胺形成能力,48 h尸胺形成量高达(766.67±2.17) mg/L,可能是四川工业泡菜尸胺含量较高的原因。文章研究结果可为四川泡菜生物胺含量的调控提供参考。

Biofilm inhibition and corrosion resistance of 2205-Cu duplex stainless steel against acid producing bacterium Acetobacter aceti

Acid producing bacterium Acetobacter aceti causes pitting corrosion of stainless steel(SS).This work investigated the enhanced resistance of 2205-Cu duplex stainless steel(DSS)against biocorrosion by A.aceti in comparison with 2205 DSS using electrochemical and surface analysis techniques.With the addition of Cu to 2205 DSS,biofilms on the 2205-Cu DSS surface were inhibited effectively.The largest pit depth on 2205-Cu DSS surface in the presence of A aceti was 2.6μm,smaller than 5.5μm for 2205 DSS surface.The i(corr)was 0.42±0.03μA cm^-2 for 2205-Cu DSS in the biotic medium,which was much lower than that for 2205 DSS(3.69±0.65μA cm^-2).All the results indicated that the A aceti biofilm was considerably inhibited by the release of Cu^2+ions from the 2205-Cu DSS matrix,resulting in the mitigation of biocorrosion by A aceti.