Exoenzyme-producing halophilic bacteria from the former Lake Texcoco: identification and production of n-butyl oleate and bioactive peptides.

Halophilic bacterias from saline soil from former Lake Texcoco were isolated, identified based on 16 rRNA and tested to produce glucolytic, nucleolytic, proteolytic and lipolytic exoenzymes. The Bacillus, Virgibacillus, Kocuria, Salinicoccus, Gracilibacillus, Halobacillus, Tenuibacillus and Nesterekonia genera where identified. Lipase/eserases and proteases from Nesterenkonia sp. and Nesterenkonia aethiopica showed halotolerant characteristics and were selected to synthesize the oleochemical n-butyl oleate and antioxidant peptides from muscle protein of common carp (Cyprinus carpio), respectively. In organic media (2,2,4-Trimethylpentane), the lipase/esterases from Nesterenkonia sp. (0.6 U/mL) and N. aethiopica (1.2 U/mL) achieved a 62.7% and 53.2% of n-butyl oleate conversion, respectively. The protein hydrolysis from muscle of common carp (C. carpio) showed a degree of hydrolysis of 4.5 ± 0.2% and 2.8 ± 0.1% when proteases from Nesterenkonia sp. and N. aethiopica were used, respectively. Three peptidic fractions ranging molecular masses between 254 and 1002 Da [M + H] show antioxidant scavenging activity, and the principal fraction with a peptide of 547.3 Da [M + H] showed an inhibition of 37.7 ± 1.8% and 16.3 ± 0.6%, when 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) were used, respectively. These findings showed that the enzymatic battery of the halophilic bacteria from former lake Texcoco can be used in hydrolysis and synthesis of molecules with applications in different fields as food technology or bioenergy.

Heterologous production of cellobiose dehydrogenases from the basidiomycete Coprinopsis cinerea and the ascomycete Podospora anserina and their effect on saccharification of wheat straw.

Cellobiose dehydrogenases (CDHs) are extracellular glycosylated haemoflavoenzymes produced by many different wood-degrading and phytopathogenic fungi. Putative cellobiose dehydrogenase genes are recurrently discovered by genome sequencing projects in various phylogenetically distinct fungi. The genomes from the basidiomycete Coprinopsis cinerea and the ascomycete Podospora anserina were screened for candidate cdh genes, and one and three putative gene models were evidenced, respectively. Two putative cdh genes were selected and successfully expressed for the first time in Aspergillus niger. CDH activity was measured for both constructions (CDHcc and CDHpa), and both recombinant CDHs were purified to homogeneity and subsequently characterised. Kinetic constants were determined for several carbohydrates including ß-1,4-linked di- and oligosaccharides. Optimal temperature and pH were 60 °C and 5 for CDHcc and 65-70 °C and 6 for CDHpa. Both CDHs showed a broad range of pH stability between 4 and 8. The effect of both CDHs on saccharification of micronized wheat straw by an industrial Trichoderma reesei secretome was determined. The addition of each CDH systematically decreased the release of total reducing sugars, but to different extents and according to the CDH concentration. Analytical methods were carried out to quantify the release of glucose, xylose and gluconic acid. An increase of glucose and xylose was measured at a low CDHcc concentration. At moderated and high CDHcc and CDHpa concentrations, glucose was severely reduced with a concomitant increase of gluconic acid. In conclusion, these results give new insights into the physical and chemical parameters and diversity of basidiomycetous and ascomycetous CDHs. These findings also demonstrated that CDH drastically influenced the saccharification on a natural substrate, and thus, CDH origin, concentration and potential enzymatic partners should be carefully considered in future artificial secretomes for biofuel applications.

Changes in the bacterial populations of the highly alkaline saline soil of the former lake Texcoco (Mexico) following flooding.

Flooding an extreme alkaline-saline soil decreased alkalinity and salinity, which will change the bacterial populations. Bacterial 16S rDNA libraries were generated of three soils with different electrolytic conductivity (EC), i.e. soil with EC 1.7 dS m(-1) and pH 7.80 (LOW soil), with EC 56 dS m(-1) and pH 10.11 (MEDIUM soil) and with EC 159 dS m(-1) and pH 10.02 (HIGH soil), using universal bacterial oligonucleotide primers, and 463 clone 16S rDNA sequences were analyzed phylogenetically. Library proportions and clone identification of the phyla Proteobacteria, Actinobacteria, Acidobacteria, Cyanobacteria, Bacteroidetes, Firmicutes and Cloroflexi showed that the bacterial communities were different. Species and genera of the Rhizobiales, Rhodobacterales and Xanthomonadales orders of the alpha- and gamma-subdivision of Proteobacteria were found at the three sites. Species and genera of the Rhodospirillales, Sphingobacteriales, Clostridiales, Oscillatoriales and Caldilineales were found only in the HIGH soil, Sphingomonadales, Burkholderiales and Pseudomonadales in the MEDIUM soil, Myxococcales in the LOW soil, and Actinomycetales in the MEDIUM and LOW soils. It was found that the largest diversity at the order and species level was found in the MEDIUM soil as bacteria of both the HIGH and LOW soils were found in it.

Phylogenetic analysis of the archaeal community in an alkaline-saline soil of the former lake Texcoco (Mexico).

The soil of the former lake Texcoco is an extreme environment localized in the valley of Mexico City, Mexico. It is highly saline and alkaline, where Na+, Cl(-), HCO3(-) and CO3(2-) are the predominant ions, with a pH ranging from 9.8 to 11.7 and electrolytic conductivities in saturation extracts from 22 to 150 dS m(-1). Metagenomic DNA from the archaeal community was extracted directly from soil and used as template to amplify 16S ribosomal gene by PCR. PCR products were used to construct gene libraries. The ribosomal library showed that the archaeal diversity included Natronococcus sp., Natronolimnobius sp., Natronobacterium sp., Natrinema sp., Natronomonas sp., Halovivax sp., "Halalkalicoccus jeotgali" and novel clades within the family of Halobacteriaceae. Four clones could not be classified. It was found that the archaeal diversity in an alkaline-saline soil of the former lake Texcoco, Mexico, was low, but showed yet uncharacterized and unclassified species.