Katiushka Arévalo-Niño

Edible Active Coatings Based on Pectin, Pullulan, and Chitosan Increase Quality and Shelf Life of Strawberries (Fragaria ananassa).

Edible active coatings (EACs) based on pectin, pullulan, and chitosan incorporated with sodium benzoate and potassium sorbate were employed to improve the quality and shelf life of strawberries. Fruits were washed, disinfected, coated by dipping, packed, and stored at 4 °C for 15 d. Application of EACs reduced (P < 0.05) weight loss and fruit softening and delayed alteration of color (redness) and total soluble solids content. In contrast, pH and titratable acidity were not affected (P > 0.05) throughout storage, and ascorbic acid content was maintained in pectin-EAC coated strawberries. Microbiological analyses showed that application of EACs reduced (P < 0.05) microbial growth (total aerobic counts, molds, and yeasts) on strawberries. Chitosan-EAC coated strawberries presented the best results in microbial growth assays. Sensory quality (color, flavor, texture, and acceptance) improved and decay rate decreased (P < 0.05) in pectin-EAC, pullulan-EAC, and chitosan-EAC coated strawberries. In conclusion, EACs based on polysaccharides improved the physicochemical, microbiological, and sensory characteristics, increasing the shelf life of strawberries from 6 (control) to 15 d (coated fruits).

A Novel Expansin Protein from the White-Rot Fungus Schizophyllum commune

A novel expansin protein (ScExlx1) was found, cloned and expressed from the Basidiomycete fungus Schizophylum commune. This protein showed the canonical features of plant expansins. ScExlx1 showed the ability to form “bubbles” in cotton fibers, reduce the size of avicel particles and enhance reducing sugar liberation from cotton fibers pretreated with the protein and then treated with cellulases. ScExlx1 was able to bind cellulose, birchwood xylan and chitin and this property was not affected by different sodium chloride concentrations. A novel property of ScExlx1 is its capacity to enhance reducing sugars (N-acetyl glucosamine) liberation from pretreated chitin and further added with chitinase, which has not been reported for any expansin or expansin-like protein. To the best of our knowledge, this is the first report of a bona fide fungal expansin found in a basidiomycete and we could express the bioactive protein in Pichia pastoris.

Characterization of Cry Proteins in Native Strains of Bacillus thuringiensis and Activity Against Anastrepha ludens1

Abstract. Bacillus thuringiensis (Berliner) strains isolated from soil of citrus orchards were tested for insecticidal activity against the Mexican fruit fly, Anastrepha ludens (Loew), a key citrus pest in Mexico. From a total of 55 soil samples, 201 isolates were selected, for a total B. thuringiensis index of 0.66. The collection was characterized through light microscopy, polyacrylamide gel electrophoresis (SDS-PAGE), and PCR analysis detecting cry2, cry4, cry10, cry11, and cry19 genes. Of the 201 isolates, 51% produced ovoid crystals, 28% adhered to the spore, 15% were pleomorphic, 3% were bipyramidal, 2% cubic, and 1% was pyramidal type. Six colonies were positive for the cry10 gene and one for the cry19 gene. SDS-PAGE of spore-crystal preparations revealed seven electrophoresis patterns. These were bioassayed against Mexican fruit fly adults, obtaining maximum mortality of 28%.

Isolation and Characterization of Entomopathogenic Fungi Obtained from Citrus-Growing Areas of Mexico

Abstract. A total of 142 soil samples was collected from different Mexican states: Campeche (13), Michoacán (15), Nuevo León (25), San Luis Potosí (25), Sinaloa (17), Sonora (17), Tabasco (5), Tamaulipas (20), and Yucatán (5). Larvae of the greater wax moth, Galleria mellonella (L.), were used as bait to detect, trap, and multiply entomopathogenic fungi in vivo. Twenty-three percent of the soil samples processed were positive for the presence of entomopathogenic fungi according to the macroscopic and microscopic characteristics: Beauveria bassiana (Bals.-Criv.) Vuill. was detected in 12% (17 isolates), Metarhizium anisopliae (Metchnikoff) Sorokin in 1% (2 isolates), and Isaria fumosorosea (Wize) in 10% (14 isolates). Genetic variability of the fungi was analyzed using the sequences of internal transcribed ribosomal genes (ITS-5.8S-ITS2) and digested with the enzyme Haelll. PCR results generated fragments of 600 bp for B. bassiana and M. anisopliae, and more than 600 bp for I. fumosorosea. Both reference strains and field isolates produced similar restriction patterns. Genera of native entomopathogenic fungi were found in the diverse citrus areas of Mexico, opening the possibility for biological control of pests affecting citrus in each region.

Evaluation of conidia production and mycelial growth in solid culture media from native strains of entomopathogenic fungi isolated from citrus-growing areas of México

It is important to know the ability of native strains to carry out the process of sporulation and growth in different conditions and to determine their possible potential as biological control of pests of agricultural importance, mainly in citrus areas. The objective of this study was to evaluate five different solid culture media for the determination of the production of conidia and mycelial growth of twenty-five native isolates from the Mexican states of Sinaloa, San Luis Potosi, Nuevo Leon and Tamaulipas, and three collection strains using five different solid culture media. The results showed no statistical significant difference between the five media tested for the production of conidia per milliliter and mycelial growth among different isolates. However between isolates a significant difference was found. For conidia per milliliter, the isolate with the highest production of conidia was HIB-4 with an average of 4.85 x 10 9 (spores/ml). With respect to mycelial growth strain Ma presented the highest value with 8.06 cm on average. Key words : Entomopathogenic fungi, esporulation, conidia, mycelial growth.

Evaluation of Potential Microencapsulated Agents for Oral Entomopathogens with Phagostimulant Activity against Spodoptera exigua (Hüber)

Abstract. The efficacy of bioinsecticides that act by ingestion can be improved using phagostimulants that increase the consumption of the pathogen. Three biopolymers, gelatin, pectin, and corn starch, with five additive phagostimulants, maize spike, fresh maize cobs, alfalfa, sorghum leaves, and cabbage, were used to form 18 microencapsulant matrices. The matrices were evaluated for feeding preferences by beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Ten neonate larvae were given a choice between two different matrices or between one matrix and a small piece of fresh cabbage used as a check. Results showed that beet armyworm larvae preferred matrices of gelatin and pectin biopolymers and additives of cabbage powder or maize spike over fresh cabbage. The best microencapsulant agents were gelatin-cabbage and gelatin-maize spike, attracting 5.47 and 5.42 larvae, respectively. The larvae preferred fresh cabbage when given a choice between fresh cabbage and a biopolymer without any phagostimulant. Phagostimulants can be added to biopesticides to increase the consumption rate and kill more pests. Gelatin was the best biopolymer and the phagostimulants maize spike and cabbage were very palatable to beet armyworm larvae.

Antibody profile to Borrelia burgdorferi in veterinarians from Nuevo León, Mexico, a non-endemic area of this zoonosis.

Objectives Lyme disease is a tick-borne disease caused by infections with Borrelia. Persons infected with Borrelia can be asymptomatic or can develop disseminated disease. Diagnosis and recognition of groups at risk of infection with Borrelia burgdorferi is of great interest to contemporary rheumatology. There are a few reports about Borrelia infection in Mexico, including lymphocytoma cases positive to B. burgdorferi sensu stricto by PCR and a patient with acrodermatitis chronica atrophicans. Veterinarians have an occupational risk due to high rates of tick contact. The aim of this work was to investigate antibodies to Borrelia in students at the Faculty of Veterinary Medicine and Zootechnics, at Nuevo León, Mexico, and determine the antibody profile to B. burgdorferi antigens. Material and methods Sera were screened using a C6 ELISA, IgG and IgM ELISA using recombinant proteins from B. burgdorferi, B. garinii and B. afzelii. Sera with positive or grey-zone values were tested by IgG Western blot to B. burgdorferi sensu stricto. Results All volunteers reported tick exposures and 72.5% remembered tick bites. Only nine persons described mild Lyme disease related symptoms, including headaches, paresthesias, myalgias and arthralgias. None of the volunteers reported erythema migrans. Nine samples were confirmed by IgG Western blot. The profile showed 89% reactivity to OspA, 67% to p83, and 45% to BmpA. Conclusions Positive sera samples shared antibody reactivity to the markers of late immune response p83 and BmpA, even if individuals did not present symptoms of Lyme arthritis or post-Lyme disease. The best criterion to diagnose Lyme disease in our country remains to be established, because it is probable that different strains coexist in Mexico. This is the first report of antibodies to B. burgdorferi in Latin American veterinarians. Veterinarians and high-risk people should be alert to take precautionary measures to prevent tick-borne diseases.

Schizophyllum commune: An unexploited source for lignocellulose degrading enzymes

Lignocellulose represents the most abundant source of carbon in the Earth. Thus, fraction technology of the biomass turns up as an emerging technology for the development of biorefineries. Saccharification and fermentation processes require the formulation of enzymatic cocktails or the development of microorganisms (naturally or genetically modified) with the appropriate toolbox to produce a cost‐effective fermentation technology. Therefore, the search for microorganisms capable of developing effective cellulose hydrolysis represents one of the main challenges in this era. Schizophyllum commune is an edible agarical with a great capability to secrete a myriad of hydrolytic enzymes such as xylanases and endoglucanases that are expressed in a high range of substrates. In addition, a large number of protein‐coding genes for glycoside hydrolases, oxidoreductases like laccases (Lacs; EC 1.10.3.2), as well as some sequences encoding for lytic polysaccharide monooxygenases (LPMOs) and expansins‐like proteins demonstrate the potential of this fungus to be applied in different biotechnological process. In this review, we focus on the enzymatic toolbox of S. commune at the genetic, transcriptomic, and proteomic level, as well as the requirements to be employed for fermentable sugars production in biorefineries. At the end the trend of its use in patent registration is also reviewed.

Genetic variability analysis of entomopathogenic fungi isolated from citrus-growing areas of Mexico

The objective of the study was to isolate and characterize genetically native fungi that remain in the soil of the diverse citrus regions of Mexico. We collected 142 soil samples from different Mexican states: Campeche (13), Michoacan (15), Nuevo Leon (25), San Luis Potosi (25), Sinaloa (17), Sonora (17), Tabasco (5), Tamaulipas (20), and Yucatan (5). Larvae of Galleria mellonella were used as bait to detect, trap and multiply entomopathogenic fungi in vivo. 23% of the soil samples processed were positive for the presence of entomopathogenic fungi according to the macroscopic and microscopic characteristics: Beauveria was detected in 12% (17 isolates), Metarhizium in 1% (2 isolates) and Isaria in 10% (14 isolates). We analyzed the genetic variability of the fungi by using the sequences of internal transcribed ribosomal genes (ITS-5.8S-ITS2) and subsequently performed the digestion with the enzyme Hae III. The results of the PCR generated fragments of approximately 600 bp for Beauveria spp., and Metarhizium spp. In the case of Isaria spp., it amplified a fragment above of 600 bp. Both reference strains and field isolates produced similar restriction patterns. Genera of native entomopathogenic fungi were found on the diverse citrus areas of Mexico; this opens the field for the biological control of pests affecting citrus in each region.