Isolation, Identification and Partial Characterization of a Lactobacillus casei Strain with Bile Salt Hydrolase Activity from Pulque.

The aim of this study was to isolate, from pulque, Lactobacillus spp. capable of survival in simulated gastrointestinal stress conditions. Nine Gram-positive rods were isolated; however, only one strain (J57) shared identity with Lactobacillus and was registered as Lactobacillus casei J57 (GenBank accession: JN182264). The other strains were identified as Bacillus spp. The most significant observation during the test of tolerance to simulated gastrointestinal conditions (acidity, gastric juice and bile salts) was that L. casei J57 showed a rapid decrease (p ≤ 0.05) in the viable population at 0 h. Bile salts were the stress condition that most affected its survival, from which deoxycholic acid and the mix of bile salts (oxgall) were the most toxic. L. casei J57 showed bile salt hydrolase activity over primary and secondary bile salts as follows: 44.91, 671.72, 45.27 and 61.57 U/mg to glycocholate, taurocholate, glycodeoxycholate and taurodeoxycholate. In contrast, the control strain (L. casei Shirota) only showed activity over tauroconjugates. These results suggest that L. casei J57 shows potential for probiotic applications.

Dynamics of carbon and nitrogen in a mixture of polycyclic aromatic hydrocarbons contaminated soil amended with organic residues.

Contamination of soil with polycyclic aromatic hydrocarbons (PAHs) through oil spills occurs frequently in Mexico. PAHs are highly resistant to degradation and restoration of these contaminated soils might be achieved by applying readily available organic material. A clayey soil was contaminated in the laboratory with different forms of PAHs, i.e. phenanthrene, anthracene and benzo(a)pyrene, and amended with maize or biosolids while production of carbon dioxide (CO2), dynamics of ammonia (NH4-), nitrate (NO3-) and PAHs were monitored. The largest CO2 production rate was found in soil added with maize and biosolids and the lowest in the unamended soil. The concentration of PAHs added to the sterilized soil did not change significantly over time and addition of organic material had no significant effect on it. The concentration of PAHs in unsterilized soil decreased sharply in the first weeks independent of addition of organic material and changes were small thereafter. After 100 days, 77% of benzo(a)pyrene was removed from soil, but 91% and 93% of phenanthrene and anthracene, respectively was removed. It was concluded that the autochthonous microbial population degraded phenanthrene, anthracene and benzo(a)pyrene, but neither biosolids nor maize accelerated the decomposition of PAHs or affected their residual concentration.

Dynamics of carbon, nitrogen and hydrocarbons in diesel-contaminated soil amended with biosolids and maize.

Contamination of soil with hydrocarbons occurs frequently when petroleum ducts are damaged. Restoration of those contaminated soils might be achieved by applying readily available organic material. An uncontaminated clayey soil sampled in the vicinity of a duct carrying diesel which ruptured recently, was contaminated in the laboratory and amended with or without maize or biosolids while production of carbon dioxide (CO(2)), dynamics of ammonia (NH(4)(+)), nitrates (NO(3)(-)), and total petroleum hydrocarbons (TPH) were monitored. The fastest mineralization of diesel, as witnessed by production of CO(2), was found when biosolids were added, but the amount mineralized after 100 days, approximately 88%, was similar in all treatments. Approximately 5 mg of the 48 mg TPH kg(-1) found in the sterilized soil at the beginning of the experiment could not be accounted for after 100 days. The concentration of TPH in the unsterilized soil decreased rapidly in all treatments, but the rate of decrease was different between the treatments. The fastest decrease was found in the soil amended with biosolids and approximately 30 mg TPH kg(-1) or 60% could not be accounted for within 7 days. The decrease in concentration of TPH at the onset of the incubation was similar in the other treatments. After 100 days, the concentration of TPH was similar in all soils and appear to stabilize at 19 mg TPH kg(-1) soil. It was concluded that biosolids accelerated the decomposition of diesel and TPH due to its large nutrient content, but after 100 days the amount of diesel mineralized and the residual concentration of TPH was not affected by the treatment applied.