L.I. Rojas-Avelizapa

Bio: L.I. Rojas-Avelizapa is an academic researcher from Instituto Politécnico Nacional. The author has contributed to research in topics: Laboratory flask & Biodegradation. The author has an hindex of 3, co-authored 6 publications receiving 51 citations.

Oil-removal enhancement in media with keratinous or chitinous wastes by hydrocarbon-degrading bacteria isolated from oil-polluted soils.

Abstract: The aim of this work was to isolate oil-degrading bacteria that use chitin or keratin as carbon sources from oil contaminated soils; and additionally to study if oil removal by these bacteria is enhanced when a chitinous or a keratinous waste is added to the culture media. To isolate the above-mentioned bacteria, 12 soil samples were collected close to an oil-well. Such soils showed unsuitable nutrients content, but their counts of heterotrophic bacteria ranged within 10(5)-10(8) CFU g(-1) soil, of which 0.1-77% corresponded to oil hydrocarbon-degrading ones. By sampling on plates, 109 oil-degrading bacterial isolates were obtained. Their keratinase and chitinase activities were then screened by plate assays and spectrophotometric methods, resulting in 13 isolates that were used to integrate two mixed cultures, one keratinolytic and the other chitinolytic. These mixed cultures were grown in media with oil, or oil supplemented with chicken-feathers or shrimp wastes. The oil-hydrocarbon removal was measured by gas chromatography. Results showed that keratinolytic bacteria were better enzyme producers than the chitinolytic ones, and that oil removal in the presence of chicken-feathers was 3.8 times greater than with shrimp wastes, and almost twice, in comparison with oil-only added cultures. Identification of microorganisms from the mixed cultures by 16S rDNA, indicated the presence of seven different bacterial genera; Stenotrophomonas, Pseudomonas, Brevibacillus, Bacillus, Micrococcus, Lysobacter and Nocardiodes. These findings suggest that the isolated microorganisms and the chicken-feather wastes could be applied to the cleaning of oil-contaminated environments, whether in soil or water.

Effect of keratinous waste addition on improvement of crude oil hydrocarbon removal by a hydrocarbon-degrading and keratinolytic mixed culture

Abstract: The aim of this work was to evaluate the effect of keratinous waste addition on oil-hydrocarbon removal, through a mixed culture of oil-degrading bacteria, with the ability to secrete keratinases. The mixed culture was grown in the media with oil, or oil supplemented with chicken-feathers as the keratinous waste. Residual oil-hydrocarbons were determined as total petroleum hydrocarbons (TPHs) and oil fractions and then quantified by GC–FID and GC–MS. Results showed that in presence of the keratinous waste, the removal of oil-hydrocarbons was 57,400 mg l −1 , meanwhile the treatment without waste presented an oil-hydrocarbons removal of 35,600 mg l −1 . The aliphatic fraction was the most removed in both treatments. In addition, chromatographic profiles indicated that the aliphatic fraction showed different degradation pattern; in the presence of keratinous wastes, the C 18 to C 28 compounds were preferably removed over the C 10 to C 17 . The addition of keratinous waste not only improved the oil-hydrocarbons removal but, it changed the removal pattern of the target hydrocarbons.

Feather waste as petroleum sorbent: a study of its structural biodegradation

Abstract: Using scanning electron microscopy (SEM), the present study evaluated the biodegradation of chicken feathers during a petroleum hydrocarbon removal process by a defined-mixed culture that pose the simultaneous abilities to remove petroleum hydrocarbons and produce keratinases in liquid culture. Biodegradation treatments were performed in Erlenmeyer flasks containing mineral media, 6% w/v of chicken feathers and 64,800 mg l -1 of petroleum hydrocarbons. Flasks were inoculated with the keratinolytic-mixed culture, which was previously obtained from a petroleum-polluted site, and then incubated at 28oC, 180 rpm during 21 days. Every 7th day, a sample was collected and fractioned; one fraction was processed to be analyzed by SEM while the residual petroleum-hydrocarbons were extracted from the other fraction and quantified by gas chromatography. Controls without inocula were processed under same conditions. The photomicrographs illustrated the different stages of the feathers 鈂 biodegradation; they are first found intact without degradation while the microorganisms from the mixed culture appear only in the supernatants. After the 7th day a remarkable colonization of the feathers begins to be observed, along with a considerable degradation observed after the 14th day of incubation.

Bioremediation of crude oil-contaminated soil: comparison of different biostimulation and bioaugmentation treatments.

Abstract: Biostimulation with inorganic fertilizer and bioaugmentation with hydrocarbon utilizing indigenous bacteria were employed as remedial options for 12 weeks in a crude oil-contaminated soil. To promote oil removal, biocarrier for immobilization of indigenous hydrocarbon-degrading bacteria was developed using peanut hull powder. Biodegradation was enhanced with free-living bacterial culture and biocarrier with a total petroleum hydrocarbon removal ranging from 26% to 61% after a 12-week treatment. Oil removal was also enhanced when peanut hull powder was only used as a bulking agent, which accelerated the mass transfer rate of water, oxygen, nutrients and hydrocarbons, and provided nutrition for the microflora. Dehydrogenase activity in soil was remarkably enhanced by the application of carrier material. Metabolites of polycyclic aromatic hydrocarbons were identified by Fourier transform ion cyclotron resonance mass spectrometry.

Stenotrophomonas and Lysobacter: ubiquitous plant-associated gamma-proteobacteria of developing significance in applied microbiology

Abstract: The exploration of new source materials and the use of alternative isolation and identification methods have led to rapid expansion in the knowledge of diversity; in Lysobacter, 11 new species having been described since 2005, and in Stenotrophomonas with six new species since 2000. The new species of Lysobacter, isolated by dilution and direct plating on standard media, differ in several key phenotypic properties from those obtained by enrichment on complex polysaccharides in the original description of the genus. Revision of the definition of the genus will be required. Both culture-dependent and culture-independent methods to assess community structure, in a variety of host and nonhost environments, have established that some species of Lysobacter are a dominant component of the microflora, where previously their presence had not been suspected. Culture-independent studies have generally not added new information on the occurrence and distribution of Stenotrophomonas maltophilia and other members of the genus, which are readily isolated on standard media from source materials. Lysobacter enzymogenes and Sten. maltophilia produce similar antibiotics and share some enzyme activities which, subject to safety considerations, may make them attractive candidates for use in biological control of plant diseases and of nematodes.

Isolation and characterization of novel strains of Pseudomonas aeruginosa and Serratia marcescens possessing high efficiency to degrade gasoline, kerosene, diesel oil, and lubricating oil.

Abstract: Bacteria possessing high capacity to degrade gasoline, kerosene, diesel oil, and lubricating oil were screened from several areas of Hokkaido, Japan. Among isolates, two strains, WatG and HokM, which were identified as new strains of Pseudomonas aeruginosa and Serratia marcescens species, respectively, showed relatively high capacity and wide spectrum to degrade the hydrocarbons in gasoline, kerosene, diesel, and lubricating oil. About 90–95% of excess amount of total diesel oil and kerosene added to mineral salts media as a sole carbon source could be degraded by WatG within 2 and 3 weeks, respectively. The same amount of lubricating oil was 60% degraded within 2 weeks. Strain HokM was more capable than WatG in degrading aromatic compounds in gasoline. This strain could also degrade kerosene, diesel, and lubricating oil with a capacity of 50–60%. Thus, these two isolates have potential to be useful for bioremediation of sites highly contaminated with petroleum hydrocarbons.

Enhancement of soil petroleum remediation by using a combination of ryegrass (Lolium perenne) and different microorganisms

Abstract: This paper aims to identify the combined effect of plant growth and different microbial strains on the enhancement of bioremediation of petroleum contaminated soil. Ryegrass ( Lolium perenne ) was planted and the microbial strains of Bacillus subtilis , Sphingobacterium multivolume , Acinetobacter radioresistens , Rhodococcus erythropolis and Pseudomonas fluorescens were used both as a single agent and mixed agent. The results show that the combination of ryegrass with mixed microbial strains gave the best result with a degradation rate of 58% after 162 d. The fractional analysis of the petroleum compounds present indicated that saturated hydrocarbon degradation occurred most with the combination of microorganisms and ryegrass; polar fraction degradation occurred most under phytoremediation and the aromatic fraction was degraded the most under microbial remediation. Higher polyphenol oxidase activity occurred in all the different treatments (when compared with the control) but lower dehydrogenase activity was found in the microbial remediation process. Denaturing gradient gel electrophoresis (DGGE) analysis indicated that a more complex microbial community was present in the combined remediation process than in the other treatments and that the different treatments tended to fall into different groups according to the treatment group in the cluster analysis of the DGGE result.

Soil Bacterial Community Shifts after Chitin Enrichment: An Integrative Metagenomic Approach

Abstract: Chitin is the second most produced biopolymer on Earth after cellulose. Chitin degrading enzymes are promising but untapped sources for developing novel industrial biocatalysts. Hidden amongst uncultivated micro-organisms, new bacterial enzymes can be discovered and exploited by metagenomic approaches through extensive cloning and screening. Enrichment is also a well-known strategy, as it allows selection of organisms adapted to feed on a specific compound. In this study, we investigated how the soil bacterial community responded to chitin enrichment in a microcosm experiment. An integrative metagenomic approach coupling phylochips and high throughput shotgun pyrosequencing was established in order to assess the taxonomical and functional changes in the soil bacterial community. Results indicate that chitin enrichment leads to an increase of Actinobacteria, γ-proteobacteria and β-proteobacteria suggesting specific selection of chitin degrading bacteria belonging to these classes. Part of enriched bacterial genera were not yet reported to be involved in chitin degradation, like the members from the Micrococcineae sub-order (Actinobacteria). An increase of the observed bacterial diversity was noticed, with detection of specific genera only in chitin treated conditions. The relative proportion of metagenomic sequences related to chitin degradation was significantly increased, even if it represents only a tiny fraction of the sequence diversity found in a soil metagenome.