Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Applied Biochemistry and Biotechnology: Part A: Enzyme Engineering and Biotechnology (v.117, #3)
Production of ethanol from cellulosic biomass by Clostridium thermocellum SS19 in submerged fermentation by Ramesh Balusu; Rama Mohan R. Paduru; G. Seenayya; G. Reddy (pp. 133-141).
Plackett-Burman design, a statistical methodology, was used to screen 23 nutrients belonging to three categories—carbon, nitrogen, and salt/mineral sources—for the production of ethanol from cellulosic biomass by Clostridium thermocellum SS19 in an aerobic submerged fermentation. In this design, just n number of experiments is required for screening n=1 variables. The experimental data were subjected to statistical analysis for calculating the regression coefficients and t-values. Filter paper, Solka Floc, corn steep liquor (CSL), cysteine HCl, magnesium chloride, and ferrous sulfate showed relatively higher regression coefficients on ethanol production and growth. Among the 23 nutrients screened, based on their performance in terms of product-promoting ability, availability, and cost, filter paper, CSL, cysteine HCl, magnesium chloride, and ferrous sulfate were identified as the most effective and, therefore, selected for inclusion in further optimization studies.
Keywords: Cellulosic biomass; Plackett-Burman design; ethanol; anaerobic fermentation; Clostridium thermocellum
Hydrogen production from propionate by Rhodopseudomonas capsulata by Xian-Yang Shi; Han-Qing Yu (pp. 143-154).
Hydrogen production from propionate at various concentrations by Rhodopseudomonas capsulata, a purple nonsulfur bacterium, was studied at a temperature of 31°C, a pH of 7.0, and an illumination intensity of 3000 Lux. Among the six levels of propionate, 3.84 g/L was found to be the optimum propionate concentration for H2 production in terms of substrate utilization efficiency, H2 percentage, cumulative H2 production, and H2 yield. A modified Gompertz equation was able to describe properly the production of H2 from propionate. A comparative study of H2 production with acetate, propionate, and butyrate at 40 mM showed that, as a substrate for H2 production by R. capsulata, propionate was better than butyrate, but less favorable than acetate.
Keywords: Hydrogen; photosynthetic bacteria; propionate; Rhodopseudomonas capsulata ; acetate; butyrate
Screening of laccase, manganese peroxidase, and versatile peroxidase activities of the genus Pleurotus in media with some raw plant materials as carbon sources by Mirjana Stajic; Limor Persky; Emanuel Cohen; Yitzhak Hadar; Ilija Brceski; Solomon P. Wasser; Eviatar Nevo (pp. 155-164).
Species of the genus Pleurotus are among the most efficient natural species in lignin degradation belonging to the subclass of ligninolytic organisms that produce laccase (Lac), Mn-dependent peroxidase (MnP), versatile peroxidase (VP), and the H2O2-generating enzyme aryl-alcohol oxidase, but not lignin peroxidases. Production of Lac and oxidation of 2,6-dimethoxyphenol (DMP) in the presence and absence of Mn2+ were detected both in submerged fermentation (SF) of dry ground mandarine peels and in solid-state fermentation (SSF) of grapevine sawdust in all investigated Pleurotus species and strains. Evidence of cultivation methods having a distinct influence on the level of enzyme activities has been demonstrated. Most of the species and strains had higher Lac activity under SSF conditions than under SF conditions. DMP oxidation in the presence and absence of Mn2+ was detected in all investigated species and strains, but was lower under SF conditions than under SSF conditions for most of them. However, relative activities of DMP oxidation in the absence of Mn2+, as percentages of activity agasint DMP in the presence of Mn2+, were higher under conditions of SF than in SSF cultures in most of the investigated species and strains. The obtained results showed that strains of different origins have different efficiently ligninolytic systems and that conditions of SSF are more favorable for ligninolytic activity than those in SF owing to their similarity to natural conditions on wood substrates.
Keywords: Pleurotus ; laccase; manganese peroxidase; versatile peroxidase; submerged fermentation; solid-state fermentation
Enzymatic degradation of trichloroethylene using enzyme extracts isolated from a bacterial consortium by Bilal El-Zahab; Liliana Meza; Teresa Cutright; Ping Wang (pp. 165-174).
Degradation of trichloroethylene (TCE) using crude enzyme extracts from a bacterial consortium was examined for wastewater treatment. The effects of pH, chemical induction, and cofactor were investigate. Enzyme extracts showed an optimal activity (3.03±0.03 mg of TCE/[mg of protein·d]) at neutral pH (6.5–7.5). In an attempt to increase the production of effective enzymes for TCE degradation, chemical induction using both toluene and TCE in the growth of the bacterium consortium was conducted. Although the induction increased the overall production of protein by about fourfold, the activity of the extracts was only slightly improved (up to 3.40 mg of TCE/[mg of protein·d]), indicating that the induction did not specifically enhance the production of TCE-degrading enzymes. Interestingly, the addition of a cofactor (up to 0.02 mg/mL), NADH, led to an initial reaction rate of 5.30±0.05 mg of TCE/(mg of protein·d). This observation demonstrated that the availability of the cofactor played an important role in determining the overall degradation reaction rates. The observations with NADH were in agreement with the assumption that toluene monooxygenases (which are NADH dependent) are the key enzymes for the degradation reactions.
Keywords: Enzymatic degradation; trichloroethylene; NADH; bioremediation; toluene monooxygenase
Enhanced expression of B-subunit of Escherichia coli heat-labile enterotoxin in tobacco by optimization of coding sequence by Tae-Jin Kang; So-Chon Han; Mi-Ok Jang; Kui-Hyeon Kang; Yong-Suk Jang; Moon-Sik Yang (pp. 175-187).
Escherichia coli heat-labile toxin (LT) is a potent mucosal immunogen and immunoadjuvant for coadministered antigens. We synthesized a gene encoding the B-subunit of LT(LTB) adapted to the coding sequence of tobacco plants and fused to the endoplasmic reticulum retention signal SEKDEL to enhance its level of expression in plants. The synthetic LTB gene was cloned into a plant expression vector adjacent to the CaMV 35S promoter and was introduced into tobacco by Agrobacterium-mediated transformation. The amount of LTB protein detected in transgenic tobacco leaves was 2.2% of the total soluble plant protein, which is approx 200-fold higher than in previous reports of native LTB gene expression in transgenic plants. Enzyme-linked immunosorbent assay indicated that plant-synthesized LTB protein bound specifically to GM1-ganglioside, suggesting that the LTB subunits formed active pentamers.
Keywords: Codon optimization; Escherichia coli heat-labile toxin; gene expression; Nicotiana tabacum ; synthetic gene