Sunday, July 29, 2007
P23

Identification of alkaline microbial biocatalytic tools isolated from Mexican industrial byproducts

Monica Sanchez-Gonzalez1, Ana Gabriela Valladares1, Allan Blanco1, Javier Gallardo1, Adelfo Escalante2, Clarita Olvera2, and Martha Suarez1. (1) Facultad de Ciencias Quimicas, Universidad Autonoma de Nuevo Leon, Ave Pedro de Alba s/n, Cd Universitaria, San Nicolas de los Garza, Nuevo León, 66400, Mexico, (2) Departamento de Ingenieria celular y biocatalisis, Instituto de Biotecnología/UNAM, Avenida Universidad 2001, Colonia Chamilpa,, Cuernavaca, 62210, Mexico

Maize tortilla and derived products are staple food of Mexico. Tortillas are elaborated by the nixtamalization process that involves alkaline cooking (in the presence of CaOH), and steeping maize grains. During the alkaline boiling process a number of organic  substances (both particulate and dissolved), and parts of the grain (mainly pericarp), are lost into the water, resulting in an organically rich medium. The alkaline cooking liquor obtained from the tortilla processing is called nejayote. Although nejayote chemical composition could favor the bacterial growth, there are few reports about the presence of microorganisms in this tortilla byproduct. We isolated six microorganisms from an industrial sample of nejayote. These Gram positive, spore forming, aerobic rods were able to grow on pH’s higher than 9 and identified as Bacillus megaterium by the 16S rDNA gene sequence and by phenotypical tests. Some strains presented 99% homology to Bacillus megaterium AC46b1 isolated from calcium hydroxyde enriched ground water. All strains produced alkaline proteases and amylases and in less proportion cellulases and xylanases. Strains MS2 and MS4 produced clear zones when grown on a medium containing methyl ferulate as the main carbon source. Furthermore, cells and culture broth of B. megaterium MS2 and MS4 hydrolyzed methyl ferulate when were incubated with the substrate under alkaline conditions, demonstrating the presence of feruloyl esterases. Our results indicate that the isolated microorganisms are important sources of alkaline biocatalytic tools.

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