Juan Manuel Sánchez-Yáñez

Influence of recycling different leachate volumes on refuse anaerobic degradation.

The aim of this work was to determine the appropriate moisture regime, attained by leachate recycling, to achieve the highest municipal solid waste (MSW) biodegradation rate. To this end, leachate characteristics, methane production rate and changes in degraded refuse were studied. Twenty laboratory-scale bioreactors were loaded with MSW from the landfill of Patzcuaro (Mexico), four were used as controls and sixteen were operated under leachate recycling to achieve moisture content regimes (%MC) of 50, 60, 70 and 80%, bioreactors operated for 264 days. Hydrolysis, acidogenic and methanogenic phases were determined and studied. ANOVA and Tukeys HDS tests revealed significant differences in leachate concentration characteristics when using different recycling volumes. Maximum methane production rate was found in the 70% MC regime, whereas the highest volume was found to produce a wash out effect in the refuse matrix. Also, the highest total volatile solids removal was found in the solid phase of the 70% MC regime.

Production of short-chain fatty acids from the biodegradation of wheat straw lignin by Aspergillus fumigatus.

The wheat straw lignin-rich fraction (WSLig-RF) can be used as a raw material for the production of metabolites for industrial use if ligninolytic mitosporic fungi are used for its biodegradation into aromatics and short-chain fatty acids (SCFAs, i.e., SCFA2-6). Although methods for the production of SCFA2-6 have been described previously, quantitative data of SCFA2-6 production have not been reported. The objectives of this study were to investigate the biodegradation of different concentrations of WSLig-RF by Aspergillus fumigatus and to identify whether SCFA2-6 production was dependent on the concentration of aromatics. A. fumigatus generated 2805mgL(-1) acetic acid when mixed with WSLig-RF at a concentration of 20gL(-1). Thus, aromatics are a substrate for the biosynthesis of SCFA2-6, and their production depends on the concentration of WSLig-RF aromatics.

Occurrence of Entomopathogenic Fungi and Parasitic Nematodes on Spodoptera frugiperda (Lepidoptera: Noctuidae) Larvae Collected in Central Chiapas, México

ABSTRACT Fall armyworm larvae (FAW), Spodoptera frugiperda (J. E. Smith) were collected from whorl-stage corn, Zea mays (L.), between the V2 and V4 stages, in 22 localities of Central, Chiapas, México, called “La Frailesca” during late Jun 2009 to determine the occurrence of native entomopathogens and parasitic nematodes, and to determine the most parasitized instars. A total of 1,247 larvae were examined in search of native biological control agents. Overall total larval mortality was 16.36%. The percent larval mortality due to entomopathogens and parasitic nematodes was 12.99%. Hexamermis sp., probably albicans Siebold (Mermitha: Mermithidae) were isolated from 105 FAW larvae (8.42%) with highest incidence from the 4th, 5th, 6th and 3rd instars, respectively. Ahyphomycete, Nomuraea rileyi Farlow (Samson), was recovered from 38 larvae (about 3.05% parasitism) with highest incidence in the 5th, 3rd, 4th, and 6th instars, respectively. Lowest percentage of FAW larval parasitism was caused by unidentified microsporidian or microsporidium (1.52%), infecting 19 larvae in the 6th, 5th and 3rd instars, respectively. First and 2nd instars did not show parasitism. This information is useful in designing future biological control programs.

Inconsistencies and ambiguities in calculating enzyme activity: The case of laccase

Laccase is a key enzyme in the degradation of lignin by fungi. Reports indicate that the activity of this enzyme ranges from 3.5 to 484,000 U L(-1). Our aim was to analyze how laccase activity is calculated in the literature, and to determine statistically whether variations in activity are due to biological properties or to inconsistencies in calculation. We found a general lack of consensus on the definition of enzyme activity, and enzymes are sometimes characterized in terms of reaction rate and specific activity. Moreover, enzyme activity is calculated using at least seven different equations. Therefore, it is critical to standardize the calculation of laccase activity in order to compare results directly.

Malassezia pachydermatis in dogs with external otitis from Monterrey, Nuevo León, México

NT of M. pachydermatis. Amplified product yielded a 600 bp product characteristic for Malassezia. Most predominant dog breeds for external otitis were Cocker Spaniel, French Poodle and Criolla. In Mexico, as well as in the state of Nuevo Leon, no documented evidence exists about the presence of this yeast in dogs with external otitis. The objective was to analyze dogs with this pathology and to inform the presence of M. pachydermatis by means of culture and amplification of D1 and D2 regions of gen 26S rRNA.