Variability among strains of Aspergillus section Nigri with capacity to degrade tannic acid isolated from extreme environments.

Tannins are polyphenolic compounds that cause astringent flavor and turbidity in food. Tannase is an enzyme that catalyzes the hydrolysis of tannins and is used in food industry. This study was conducted to determine the genetic variability and the tannase alleles variation in fungal strains isolated from soil and plants at five extreme areas of Coahuila, México. Two screening assays under 1 and 20 % of tannic acid were performed, with the isolations. In these assays, it was possible to identify 756 and 128 fungal strains, respectively. The major fungal variability was observed in "Cuatro Ciénegas" with 26 strains. The microorganisms were distributed in 11 groups, which correspond to Aspergillus section Nigri. AN7 and AN1 groups showed the major number of isolates from "Paila" and "Cuatro Ciénegas" locations, respectively. In the last location, the major diversity and specific richness were found. But in "Ojo Caliente," tannase allele conservations were observed.

Utilization of molasses and sugar cane bagasse for production of fungal invertase in solid state fermentation using Aspergillus niger GH1.

Agro-industrial wastes have been used as substrate-support in solid state fermentation for enzyme production. Molasses and sugarcane bagasse are by-products of sugar industry and can be employed as substrates for invertase production. Invertase is an important enzyme for sweeteners development. In this study, a xerophilic fungus Aspergillus niger GH1 isolated of the Mexican semi-desert, previously reported as an invertase over-producer strain was used. Molasses from Mexico and Cuba were chemically analyzed (total and reducer sugars, nitrogen and phosphorous contents); the last one was selected based on chemical composition. Fermentations were performed using virgin and hydrolyzate bagasse (treatment with concentrated sulfuric acid). Results indicated that, the enzymatic yield (5231 U/L) is higher than those reported by other A. niger strains under solid state fermentation, using hydrolyzate bagasse. The acid hydrolysis promotes availability of fermentable sugars. In addition, maximum invertase activity was detected at 24 h using low substrate concentration, which may reduce production costs. This study presents an alternative method for invertase production using a xerophilic fungus isolated from Mexican semi-desert and inexpensive substrates (molasses and sugarcane bagasse).

Nucleotide and amino acid variations of tannase gene from different Aspergillus strains.

Tannase is an enzyme that catalyses the hydrolysis of ester bonds present in tannins. Most of the scientific reports about this biocatalysis focus on aspects related to tannase production and its recovery; on the other hand, reports assessing the molecular aspects of the tannase gene or protein are scarce. In the present study, a tannase gene fragment from several Aspergillus strains isolated from the Mexican semidesert was sequenced and compared with tannase amino acid sequences reported in NCBI database using bioinformatics tools. The genetic relationship among the different tannase sequences was also determined. A conserved region of 7 amino acids was found with the conserved motif GXSXG common to esterases, in which the active-site serine residue is located. In addition, in Aspergillus niger strains GH1 and PSH, we found an extra codon in the tannase sequences encoding glycine. The tannase gene belonging to semidesert fungal strains followed a neutral evolution path with the formation of 10 haplotypes, of which A. niger GH1 and PSH haplotypes are the oldest.

Utilization of molasses and sugar cane bagasse for production of fungal invertase in solid state fermentation using Aspergillus niger GH1

Agro-industrial wastes have been used as substrate-support in solid state fermentation for enzyme production. Molasses and sugarcane bagasse are by-products of sugar industry and can be employed as substrates for invertase production. Invertase is an important enzyme for sweeteners development. In this study, a xerophilic fungus Aspergillus niger GH1 isolated of the Mexican semi-desert, previously reported as an invertase over-producer strain was used. Molasses from Mexico and Cuba were chemically analyzed (total and reducer sugars, nitrogen and phosphorous contents); the last one was selected based on chemical composition. Fermentations were performed using virgin and hydrolyzate bagasse (treatment with concentrated sulfuric acid). Results indicated that, the enzymatic yield (5231 U/L) is higher than those reported by other A. niger strains under solid state fermentation, using hydrolyzate bagasse. The acid hydrolysis promotes availability of fermentable sugars. In addition, maximum invertase activity was detected at 24 h using low substrate concentration, which may reduce production costs. This study presents an alternative method for invertase production using a xerophilic fungus isolated from Mexican semi-desert and inexpensive substrates (molasses and sugarcane bagasse).