一株芽孢杆菌的分子鉴定及初步应用条件探究

引言嗜盐菌是生活在高盐环境中的细菌,多生长于盐湖、盐碱湖、死海、盐场和海洋中,腌鱼、咸肉等盐制品上也常有存在。通常嗜盐菌生长在盐浓度大于0.2mol.L-1的环境中[1]。我国西藏、青海     

异养产油单针藻的生长、代谢及脂肪酸组成的变化

单针藻是制备生物柴油较好的原料。以产油单针藻为对象,研究了单针藻在异养培养中生长、代谢的特性及脂肪酸组成变化。结果表明,Richards模型能够较好拟合藻细胞的生长与培养时间的关系。建立了微藻细胞对硝酸盐、磷酸盐的代谢模型,得出藻细胞生物量对硝酸盐、磷酸盐的得率系数分别为5.319 g/g、500 g/g。生长过程中脂肪酸组成变化的分析表明,延长藻细胞的培养稳定期可增加C18∶1的含量。     

Biosorption of mercury and lead by aqueous Streptomyces VITSVK9 sp. isolated from marine sediments from the bay of Bengal,India

Toxic heavy metals are increasingly accumulating in the environment worldwide and are considered to be life threatening contaminants. The biosorption of mercury and lead by marine actinomycetes isolated from marine sediment collected from the Bay of Bengal coast of Puducherry, India, was evaluated. The maximum tolerance concentration (MTC) of Streptomyces sp. was determined by a well diffusion method and a broth dilution method. The effects of the initial metal ion concentration, the pH and the biomass dosage on the biosorption of mercury and lead ions were investigated. The MTC of the isolate to metals was 200 mg·L^-1 for mercury and 1800 mg·L^-1 for lead. At neutral pH, the isolate had a maximum biosorption of metal ions of 200 mg·L^-1 and 150 mg·L^-1 for mercury and lead respectively. Fourier transform infrared (FTIR) absorption spectra showed the chemical interactions between the functional groups in the biomass such as hydroxyl (-OH), amine (-NH₂), carboxyl (-COOH) and the metal ions. The isolate was further characterized by molecular taxonomy and identified as a member of the genus Streptomyces. Based on the phenotypic and phylogenetic analysis, the strain was classified as a new species of the genus Streptomyces and designated as Streptomyces VITSVK9 sp. (HM137310). A blast search of the 16S rDNA sequence of the strain showed the most similarity (95%) with Streptomyces sp. A515 Ydz-FQ (EU384279). Based on the results, it can be concluded that this marine Streptomyces could be used as a biosorbent for the removal of heavy metal ions from aqueous environments.     

Decolourisation and treatment of pulp and paper mill effluent by lignin‐degrading Bacillus sp.

Three lignin‐degrading bacterial strains, identified as Paenibacillus sp., Aneurinibacillus aneurinilyticus and Bacillus sp. have been examined for the treatment of pulp and paper mill effluent. The results of this study revealed that all three bacterial strains effectively reduced colour (39–61%), lignin (28–53%), biochemical oxygen demand (BOD) (65–82%), chemical oxygen demand (COD) (52–78%) and total phenol (64–77%) within six days of incubation. However, the highest reduction in colour (61%), lignin (53%), BOD (82%) and COD (78%) was recorded by Bacillus sp. while, maximum reduction in total phenol (77%) was recorded with Paenibacillus sp. treatment. Significant reduction in colour and lignin content by these bacterial strains was observed after two days of incubation, indicating that bacterium initially utilized growth supportive substrates and subsequently chromophoric compounds thereby reducing lignin content and colour in the effluent. The total ion chromatograph (TIC) of compounds present in the ethyl acetate extract of control and bacterial treated samples revealed the formation of several lignin‐related aromatic compounds. The compounds identified in extracts of treated samples by Paenibacillus sp were t‐cinnamic acid and ferulic acid, while 3‐hydroxy‐4‐methoxyphenol, vanillic acid and vanillin acid by A. aneurinilyticus and gallic acid and ferulic acid by Bacillus sp. respectively indicating the degradation of lignin present in the effluent. The identified compounds obtained after different bacterial treatments were found to be strain‐specific. Among these identified compounds, ferulic acid, vanillic acid and vanillin could have immense value for their use in preservatives and in the food flavour industry. Copyright © 2007 Society of Chemical Industry     

Characterization of linear low‐density polyethylene/poly(vinyl alcohol) blends and their biodegradability by Vibrio sp. isolated from marine benthic environment

Increasing amounts of plastic waste in the environment have become a problem of gigantic proportions. The case of linear low‐density polyethylene (LLDPE) is especially significant as it is widely used for packaging and other applications. This synthetic polymer is normally not biodegradable until it is degraded into low molecular mass fragments that can be assimilated by microorganisms. Blends of nonbiodegradable polymers and biodegradable commercial polymers such as poly (vinyl alcohol) (PVA) can facilitate a reduction in the volume of plastic waste when they undergo partial degradation. Further, the remaining fragments stand a greater chance of undergoing biodegradation in a much shorter span of time. In this investigation, LLDPE was blended with different proportions of PVA (5–30%) in a torque rheometer. Mechanical, thermal, and biodegradation studies were carried out on the blends. The biodegradability of LLDPE/PVA blends has been studied in two environments: (1) in a culture medium containing Vibrio sp. and (2) soil environment, both over a period of 15 weeks. Blends exposed to culture medium degraded more than that exposed to soil environment. Changes in various properties of LLDPE/PVA blends before and after degradation were monitored using Fourier transform infrared spectroscopy, a differential scanning calorimeter (DSC) for crystallinity, and scanning electron microscope (SEM) for surface morphology among other things. Percentage crystallinity decreased as the PVA content increased and biodegradation resulted in an increase of crystallinity in LLDPE/PVA blends. The results prove that partial biodegradation of the blends has occurred holding promise for an eventual biodegradable product. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012