Carlos Huitrón

Universidad Nacional Autónoma de México, Mexico City, The Federal District, Mexico

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Publications (15)31.57 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Agave tequilana fructans are the source of fermentable sugars for the production of tequila. Fructans are processed by acid hydrolysis or by cooking in ovens at high temperature. Enzymatic hydrolysis is considered an alternative for the bioconversion of fructans. We previously described the isolation of Aspergillus niger CH-A-2010, an indigenous strain that produces extracellular inulinases. Here we evaluated the potential application of A. niger CH-A-2010 inulinases for the bioconversion of A. tequilana fructans, and its impact on the production of ethanol. Inulinases were analyzed by Western blotting and thin layer chromatography. Optimal pH and temperature conditions for inulinase activity were determined. The efficiency of A. niger CH-A-2010 inulinases was compared with commercial enzymes and with acid hydrolysis. The hydrolysates obtained were subsequently fermented by Saccharomyces cerevisiae to determine the efficiency of ethanol production. Results indicate that A. niger CH-A-2010 predominantly produces an exo-inulinase activity. Optimal inulinase activity occurred at pH 5.0 and 50 °C. Hydrolysis of raw agave juice by CH-A-2010 inulinases yielded 33.5 g/l reducing sugars, compared with 27.3 g/l by Fructozyme(®) (Novozymes Corp, Bagsværd, Denmark) and 29.4 g/l by acid hydrolysis. After fermentation of hydrolysates, we observed that the conversion efficiency of sugars into ethanol was 97.5 % of the theoretical ethanol yield for enzymatically degraded agave juice, compared to 83.8 % for acid-hydrolyzed juice. These observations indicate that fructans from raw Agave tequilana juice can be efficiently hydrolyzed by using A. niger CH-A-2010 inulinases, and that this procedure impacts positively on the production of ethanol.
    Journal of Industrial Microbiology 11/2012; · 1.80 Impact Factor
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    ABSTRACT: Pectin lyases cleave the internal glycosidic bonds of pectin by β-elimination, producing non-saturated galacturonic oligomers. Genetic improvement of pectin lyase-overproducing strains is still necessary to improve industrial processes based on this enzyme. In the present study hybrids were obtained by protoplast fusion between mutant pectinolytic Aspergillus flavipes and Aspergillus niveus CH-Y-1043 strains. Prototrophic segregants showed different isoenzymatic profiles and produced increased levels of pectin lyase in cultures containing lemon peel as a sole carbon source. Hybrid HZ showed an increase of 450% and 1300% in pectin lyase production compared with that of A. niveus CH-Y-1043 and A. flavipes, respectively. Pectin lyase produced by the hybrid HZ was partially purified and used for the hydrolysis of orange peel. Pectin lyase was able to hydrolyze 56% of orange peel biomass. However, addition of 2 RFU and 20 U of endo- and exo-polygalacturonase, respectively, induced the hydrolysis of 92% of orange peel solids. In conclusion HZ is a pectin lyase-overproducing hybrid with potential applications in the pectin industry.
    Enzyme and Microbial Technology 03/2009; · 2.97 Impact Factor
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    ABSTRACT: To investigate the prevalence of mucosal autoantibodies to survivin in patients with human papillomavirus (HPV)-associated cervical cancer and precursor lesions. Cervical mucus from 117 HPV-associated cervical cancer, 102 high-grade squamous intraepithelial lesion (HSIL), 107 low-grade SIL (LSIL), and 80 normal controls were tested by ELISA using either full length recombinant survivin or survivin-derived peptides. Survivin expression in cervical tissue biopsies was studied by Western Blotting. Cervical mucus from 33 cervical cancer (28.2%), 17 HSIL (16.6%), and 8 LSIL (7.4%) patients reacted with recombinant survivin. The IgA-class antibody response was significantly higher than that observed in the normal controls. The level of mucosal anti-survivin response was associated to the level and intensity of survivin expression in the different lesions. Finally, reactivity against a survivin Nt-derived peptide was found more frequently than reactivity against a Ct-derived peptide. IgA-class autoantibodies against survivin are present in a substantial proportion of cervical mucus from patients with HPV-associated cervical cancer, and precursor lesions. Mucosal anti-survivin response is positively associated with the level of survivin expression and the grade of cervical lesion.
    Autoimmunity 03/2007; 40(1):66-72. · 2.75 Impact Factor
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    ABSTRACT: Methylmalonyl-coenzyme A (CoA) mutase, methylmalonyl-CoA decarboxylase and NADP+-isocitrate dehydrogenase activity profiles were determined in Saccharopolyspora erythraea CA340, an erythromycin producer, grown in glucose or ammonium chloride. Results show that methylmalonyl-CoA mutase and isocitrate dehydrogenase activities were associated with growth, while methylmalonyl-CoA decarboxylase maximal activity was observed at stationary phase. Isocitrate dehydrogenase synthesis was stimulated by glucose and repressed by ammonium; glucose affected negatively the synthesis of methylmalonyl-CoA mutase, whereas methylmalonyl-CoA decarboxylase production was not affected by carbon or nitrogen sources. These results suggested that the negative effect of glucose or ammonium on erythromycin production could be due, in part, to lower pools of succinyl-CoA and methylmalonyl-CoA.
    FEMS Microbiology Letters 01/2006; 164(1):77 - 82. · 2.72 Impact Factor
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    ABSTRACT: Debate continues over the physical characteristics and even the existence of arginase isoenzymes. This paper gives additional support for such multiplicity and reports differences in physical characteristics among the various forms.After 2500–5000-fold purification of rat liver arginase, three molecular forms were separated on carboxymethyl-cellulose columns and were purified 2500–5000-fold, 800–1000-fold and 600–1000-fold, respectively. The molecular forms have also been identified by chromatography in the supernatant of tissue extracts. The isolation of these molecular forms by affinity chromatography, using Sepharose-lysine as a competitive inhibitor of arginase, shows only one main form, however.Kinetic studies were done for two of the molecular forms isolated, specifically the activation energy (Ea) the energy of denaturatization (Ed), Km, pH and the effect of divalent cations were determined. Significant differences were found for the Ea, between the two molecular forms. The isolated isoenzymes are cationic at pH 5.5 and pH 8.8. However, they show different mobilities in electrophoresis. The molecular weight determination by gel filtration yields a value of 110000 to 115000 for both forms. The use of thin-layer immunochromatography plates, a combination of molecular weight and immunodiffusion technique, gave only one peak with the same molecular weight as that determined by gel filtration. The immunological studies showed that the isoenzymes have similar antigenic determinants.
    European Journal of Biochemistry. 03/2005; 49(2):457 - 468.
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    ABSTRACT: Activation of the interleukin-2 receptor (IL-2R) induces signalling cascades promoting T cell proliferation. However, signal transduction pathways triggered in IL-2R-expressing solid tumours are unknown. This report shows that human papillomavirus (HPV)-associated cervical cancer cells express an IL-2R composed of beta and gamma chains (IL-2Rbetagamma), and that IL-2-mediated activation increases the phosphorylation of JAK3 and STAT5, stimulating cell proliferation. Interestingly, endogenous IL-2 is not produced by these cells, suggesting the activation of IL-2Rbetagamma by an alternative mechanism. Accordingly, we found that Stem Cell Factor (SCF)-activated c-Kit induces phosphorylation of the IL-2Rbeta chain in the absence of IL-2. Moreover, inhibition of IL-2Rbeta phosphorylation by blocking c-Kit tyrosine kinase activity abolishes both, IL-2 and SCF-mediated proliferation. Thus, these results demonstrate that IL-2 triggers a JAK3/STAT5 cascade in HPV-associated cervical cancer cells expressing IL-2Rbetagamma, and that this receptor can be alternatively activated by SCF-activated c-Kit in the absence of IL-2.
    Cellular Signalling 12/2004; 16(11):1239-47. · 4.47 Impact Factor
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    ABSTRACT: The taxonomic position of a thermophilic actinomycete strain isolated from soil was examined using a polyphasic approach. The strain, designated CH-M-1035T, was assigned to the genus Streptomyces on the basis of chemical and morphological criteria. It formed Rectiflexibiles aerial hyphae that carried long chains of rounded, smooth spores. The almost complete nucleotide sequence of the 16S rRNA gene of strain CH-M-1035T was determined and its comparison with the 16S rDNA sequences of previously studied streptomycetes confirmed the assignment of the novel strain to the genus Streptomyces. Strain CH-M-1035T clustered with species belonging to the Streptomyces thermodiastaticus clade in the 1 6S-rDNA-based phylogenetic tree. However, the phenotypic properties of strain CH-M-1035T differed from those of the recognized species within this clade. Therefore, it is proposed that strain CH-M-1035T be classified as a novel species within the genus Streptomyces, as Streptomyces mexicanus (type strain CH-M-1035T =DSM 41796T =BM-B-384T =NRRL B-24196T).
    International Journal of Systematic and Evolutionary Microbiology 02/2003; 53(Pt 1):269-73. · 2.80 Impact Factor
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    ABSTRACT: Streptomyces sp. DSM 41796 produced four major extracellular xylanases with Mr of 145, 120, 60 and 45 kDa. Those of 145 and 60 kDa formed a heterodimer. All xylanases, except that of 120 kDa, were induced by xylose, d-arabinose or sucrose, while commercial xylans induced the 60 kDa xylanase in a major proportion than others, and sugar-cane bagasse pith or lemon peel induced predominantly the 45 kDa xylanase.
    Biotechnology Letters 08/2002; 24(18):1473-1476. · 1.74 Impact Factor
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    ABSTRACT: The specificity of induction of β-xylosidase and endoxylanase from Streptomyces sp. CH-M-1035 was investigated using mono-, di- and poly-saccharides, among other compounds. This microorganism was able to grow on all carbon sources except cellulose microcrystalline and methyl-β-D-xylopyranoside. β-Xylosidase was induced by larchwood xylan, birchwood xylan, oat spelts xylan and D-xylose. Basal levels of activity were obtained in sucrose, lactose, maltose and pectin. Endoxylanase activity was induced in presence of xylans, D-xylose, sucrose and D-arabinose. Both enzymes, β-xylosidase and endoxylanase, were repressed by the addition of glucose, glycerol and succinic acid to the culture medium containing 1% birchwood xylan. On the other hand, addition of methyl-β-D-xylopyranoside in the same conditions induced β-xylosidase but not endoxylanase synthesis. An unexpected stimulatory effect was observed on β-xylosidase biosynthesis when pyruvic acid was added to the culture medium independently of the xylan used.
    Journal of Biotechnology. 01/1996;
  • Oscar Garcia-Kirchner, Carlos Huitron
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    ABSTRACT: Filter paper, carboxymethylcellulase, β-glucosidase, and xylanase activities were determined and compared to cellulases originating fromAureobasidium sp. (Ab),Penicillium sp. (Pe), andAspergillus terreus (At). The formation of total reducing sugar was measured as a function of time for the hydrolysis of the native sugar cane bagasse pith using culture filtrates with the same quantity of extracellular protein content from Ab, Pe, At, or from the following mixtures Ab:Pe/ Ab:At and Pe:At at different volumetric ratios. The saccharification progress indicated a synergistic effect for the mixture of all the enzymes, the highest being in the 40:60 relation of Pe and At, respectively. The synergistic action has been assigned to a better balance of endo- and exoglucanases in this system and essentially to the addition of β-glucosidase and xylanases from At to Pe cellulases.
    Applied Biochemistry and Biotechnology 01/1996; · 1.69 Impact Factor
  • European Journal of Biochemistry 12/1974; 49(2):457-68. · 3.58 Impact Factor
  • R Palacios, C Huitrón, G Soberón
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    ABSTRACT: It has been previously postulated that the enzymes that participate in urea biosynthesis should be physically linked. The possibility that arginase keeps a close functional relation with the arginine formation sites has been explored in rat liver homogenate by generating arginine from two sources: I) labelled citrulline and aspartic acid, and II) hippuryl arginine and carboxypeptidase B. The results obtained show that the former is preferentially hydrolysed, which is in accordance with the stated postulate.
    Biochemical and Biophysical Research Communications 03/1970; 38(3):438-43. · 2.28 Impact Factor
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    R Palacios, C Huitrón, G Soberón
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    ABSTRACT: 1. The effects of 19 bivalent cations on the activity, stability and capacity to hydrolyse endogenous arginine of axolotl liver arginase were studied. 2. It was found that Fe(2+), Co(2+), Ni(2+) and Zn(2+), as well as Mn(2+), stabilize the enzyme and render it able to hydrolyse endogenous arginine. 3. By using different concentrations of Co(2+) and Ni(2+) it was possible to dissociate the effect of each of the metal ions on the activity and stability of arginase from that on its capacity to hydrolyse endogenous arginine. 4. The effects of Mn(2+), Co(2+) and Ni(2+) on the activity and stability of arginase in the homogenate were also observed with purer preparations of the enzyme. 5. It is suggested that the capacity to hydrolyse endogenous arginine is a consequence of the integration of arginase with the arginine-formation sites.
    Biochemical Journal 10/1969; 114(3):449-54. · 4.78 Impact Factor
  • C Huitrón, R Palacios, G Soberón
    Boletín de estudios médicos y biológicos 28(11-12):391-401.

Publication Stats

86 Citations
31.57 Total Impact Points


  • 1970–2012
    • Universidad Nacional Autónoma de México
      • Departament of Molecular Biology and Biotechnology
      Mexico City, The Federal District, Mexico
  • 2004
    • National Pedagogic University (Mexico)
      Ciudad de México, The Federal District, Mexico
  • 1996
    • National Polytechnic Institute
      Villa Gustavo A. Madero, The Federal District, Mexico