ABSTRACT
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).
ABSTRACT
The aim of this study was to evaluate the fermentation of dietary fiber from green bean (Phaseolus vulgaris) and prickly pear shell (Opuntia ficus-indica) by Lactobacillus acidophilus LA-5 and Bifidobacterium bifidum 450B growing as mono-culture and co-culture, the fermentation products, and proteins expressed during this process. The analysis of the fermentation profile showed a major growth of bacteria in the culture media of each dietary fiber supplemented with glucose, and particularly B. bifidum 450B at 48 h showed the highest growth. In the case of the co-culture, the growth was lower indicating the possible negative interaction between L. acidophilus LA-5 and B. bifidum 450B and may be due to the less amount of carbohydrates and the high content of non-soluble fiber that affected the nutrients availability for the bacterial strains. The pH changes indicated the presence of short-chain fatty acids (SCFAs), being acetate (46-100%) the main SCFA. Changes in the proteome concerned proteins that are involved in carbohydrate and other carbohydrate pathways. The characterization of the bacteria according to the growth, metabolites, and proteins expressed allows understanding the response to the change of environmental conditions and could be useful to understand L. acidophilus LA-5 and B. bifidum 450B strains' adaptation to specific applications.
