| With the development of society,it is very imperative to find a clean and renewable energy to solve urgent problems such as environment pollution and energy shortage.It is well known that H2 is considered as a kind of ideal energy because it is clean,renewable and has higher combustion valve than others.Biohydrogen production has bright prospect to realize industrialization and it is superior to other H2 producing methods for its high efficiency,simple equipment,renewable resources and wastes.Up to now,however,the biohydrogen commercial process has not been realized because the high cost and low efificiency.Therefore,it is an important to screen the H2 producing micro-organisms with higher conversion rate and wider ranges of substrate utilization.In this paper,16 H2 producing strains were screened from the bottom of Shanghai Botanical Garden river sludge by anaerobic culture method.After morphological analysis,physiological and biochemical tests and 16S rDNA sequence analysis,one strain with the highest volumetric H2 production was identified as an enterobacter aerogenes and named as Enterobacter aerogenes EB-06,which was used for subsequent experiments.In order to optimize the cultural conditions and the medium composition,the H2 production characteristics of EB-06 were investigated when glucose was the only substrate.The experimental results showed that the production yield of H2 under anaerobic condition was 2.3 times higher than under the micro-oxygen condition.The optimum temperature for cell growth and H2 production were 37?and 41?,respectively.Through batch cultivation,it was known that the optimum unit volume H2 production was obtained at pH value of 8.0 which is 51.08mmol/L,while the optimum amount of H2 yeild 0.86molH2/mol Glucose was gotten at pH 5.0.When glucose was the only substrate,the production yield of H2 decreased with the initial glucose concentration.When the initial glucose concentration was 10g/L,the maximum H2 yield was 0.53mol H2/mol Glucose.The higher initial glucose concentration could inhibit the H2 yield.When glucose concentration was about 20g/L,the maximum volume H2 yield in dark fermentation and the maximum specific H2 production rate were 47.00mmol H2/L and 9.40mmol H2/gDCW·h,respectively.Metal ions could affect the H2 production metabolism through the interaction,with metal enzymes.The ex perimental result showed that the optimum Fe2+ concentration is 50mg/L.It was also found that the strain EB-06 could consume the monosaccharide,disaccharide and polysaccharide.The largest amount of H2 could be produced by EB-06 when glycerol was consumed as the only carbon source.It was generally kinown that Enterobacter aerogenes could use glycerol to produce ethanol and H2.The optimal condition of H2 production and the characteristics of H2 production by strain EB-06 when glycerol was the only carbon source were studied in this paper.This process could not only produce clean energy H2,but also consume the by-product of bio-diesel industry glycerol.The effects of the initial pH value,initial glycerol concentration,inoculation amount and C/N ratio on H2 production of strain EB-06 were investigated by single factor experiments.The results showed that the optimum volume H2 yield was about 83.76mmolH2/L when the initial pH was 7.0.The optimum specific H2 production rate was about 41.47mmolH2/gDCW·h when the initial glycerol concentration was 40g/L.It was found that the H2 yield under 4%inoculation amount was 2 times higer than that 0.5%inoculation.The yield per unit volume of H2 production decreased with the increase of C/N ratio.It was 82.10 mmolH,/L when C/N ratio was 1/1.While it was decreased to 39.60mmolH2/L when C/N ratio was 2/1.The optimum H2 production condition was obtained through the orthogonal experimental and shown as follows:the initial glycerol concentration lOg/L,the initial pH value 5.0,C/N ratio 5/3.The optimum H2 yield was obtained as 1.07 mmolH2/mol Glycerol.The result was close to the highest yield 1.12mol H2/mol Glycerol from the reported literature. |
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