Phylogeny and polycyclic aromatic hydrocarbons degradation potential of bacteria isolated from crude oil-contaminated site.

This study employed the use of 16S rRNA gene sequence analysis to identify three of four native bacterial strains isolated from crude oil-contaminated site in Poza Rica, Veracruz, Mexico. The identified bacteria were Ochrobactrum intermedium, Pandoraea pnomenusa and Ochrobactrum sp., but SA2-09 strain was not identified. The ability of the isolates to degrade polycyclic aromatic hydrocarbons (PAHs) was evaluated at 31.61 and 54.52 mg/kg PAHs in soil, when used as crude oil in soil microcosm during 80 days of incubation at 30°C. The results demonstrated that O. intermedium biodegraded many PAHs, including the high molecular weight (HMW) PAHs fluoranthene (100% equivalent 0.24 mg/kg), benzo [b] fluoranthene (81.8% equal 0.18 mg/kg), Benzo[a]pyrene (87.0%, 0.20 mg/kg) and Benzo[g,h,i]perylene (52.7%, 0.39 mg/kg). P. pnomenusa had a degradation profile of HMW PAHs, which was similar to O. intermedium, while Ochrobactrum sp. and the strain SA-09 exhibited lower degradation rates of HMW.

Application of 2III7-3 fractional factorial experimental design to enhance enzymatic activities of Pleurotus ostreatus with high concentrations of polychlorinated biphenyls.

A 2(III)(7-3) fractional factorial experimental design was used to establish 16 culture media, with and without PCBs to enhance the activities of laccase (Lac), manganese peroxidase (MnP), and versatile peroxidase (VP) produced by the white rot fungus Pleurotus ostreatus. The culture was added to 10,000 mg L(-1) of transformer oil, containing 71% of the identified Arochlor 1242. The culture conditions were established with eight variables at two values (levels); pH (4 and 6), agitation (100 and 200 rpm), CuSO(4) (150 and 250 mg L(-1)), MnSO(4) (50 and 200 mg L(-1)), Tween 80 (13 and 3500 mg L(-1)), wheat straw (0 and 2.5 g L(-1)), sugarcane bagasse (0 and 2.5 g L(-1)),and Arochlor 1242 (0 and 7100 mg L(-1)) at 4, 8, 12, 16 and 20 days old culture. Laccase activity was enhanced at a high value of pH and low value of agitation (P<0.001) and correlated positively (R(2)= 0.9; α=0.05) with the removal of polychlorinated biphenyls (PCBs). VP activity was enhanced 27-fold with PCBs, Tween 80 and pH. The MnP activity was increased 1.2-fold with PCBs. The fractional factorial experimental design methodology allowed us to determine the P. ostreatus culture media conditions to enhance Lac and VP activities for efficient removal of Arochlor 1242 (one of the most recalcitrant organochloride pollutants). The factors that shown the greatest effect on Lac activity were: pH, agitation and high concentrations of Arochlor 1242.

Kinetics of infective juvenile production of the entomopathogenic nematode Steinernema carpocapsae in submerged monoxenic culture.

The effects of culture medium formulations on the kinetics of infective juvenile (IJ) production of the entomopathogenic nematode Steinernema carpocapsae in submerged monoxenic culture, were studied at the cylindrical-bottle scale using six culture media containing agave juice from Agave spp. among other ingredients. The IJ production kinetics was well modelled through a re-parameterised 3-parameter Gompertz model with kinetic parameters: IJ-lag phase lambda (IJ) (day), maximum IJ-stage production rate m (max )(day(-1)), and IJ-multiplication factor (C (IJ)/C (IJ,0))(max)(-). The variation of lambda (IJ) was not very important within fermentations (10.3-16.2 days); nonetheless, important effects were observed on m (max) (32.8-241.2 days(-1)) and (C (IJ)/C (IJ,0))(max) (66(-) to 611.4(-)). Particularly, maximum values of m (max) and (C (IJ)/C (IJ,0))(max) were obtained in medium A4 (0.276 l l(-1) agave juice, 17 g l(-1) yeast extract, 12 g l(-1) dried egg yolk, 0.025 l l(-1) corn oil). Also, the maximum IJ concentration (249,444 per ml) was achieved in A4-fermentations.