Sustainable use of giant reed to produce industrialized enzymes.

The giant reed (Arundo donax) is a fast-growing plant adapted to different climatic and soil conditions; although its origin is Asian, the species has spread throughout the world. During its development, it consumes three times more water than typical native vegetation and is responsible for changing the landscape of riparian areas; the high biomass productivity and the annual harvest period make this crop an alternative to produce and/or extract industrial bioproducts. The main objective of this research was to evaluate the feasibility of using giant reed in a bioprocess that produces enzymes by a solid-state fermentation experiment, four fungal species were tested (Aspergillus niger GH1, Aspergillus niger PSH, Trichoderma harzianum, and Rhizopus oryzae); enzyme activities were performed using reported methodologies varying only reaction volumes. The A. niger GH1 and PSH strains were the best adapted to the plant material, A. niger GH1 was capable to produce 4 of the 5 evaluated enzymes (cellulase-endoglucanase (174.39 ± 19.62 U/L), xylanase (1313.31 ± 39.25 U/L), invertase (642.22 ± 23.55 U/L), and polyphenol oxidase (6094.01 ± 306.54) while A. niger PSH was able to produce 3 of the 5 evaluated enzymes (cellulase-endoglucanase (147.09 ± 13.88 U/L), xylanase (1307.76 ± 31.40 U/L), and invertase (603.92 ± 3.14 U/L).

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.