Abstract
The bioprospection for cellulase and protease producers is a promise strategy for the discovery of potential biocatalysts for use in hydrolysis of lignocellulosic materials as well as proteic residues. These enzymes can increment and turn viable the production of second generation ethanol from different and alternative sources. In this context, the goal of this study was the investigation of cellulolytic and proteolytic abilities of bacteria isolated from the gastrointestinal tract of a hippopotamus as well as from its composting process. It is important to highlight that hippopotamus gastrointestinal samples were a non-typical sources of efficient hydrolytic bacteria with potential for application in biotechnological industries, like biofuel production. Looking for this, a total of 159 bacteria were isolated, which were submitted to qualitative and quantitative enzymatic assays. Proteolytic analyzes were conducted through the evaluation of fluorescent probes. Qualitative assays for cellulolytic abilities revealed 70 positive hits. After quantitative analyzes, 44 % of these positive hits were selected, but five (5) strains showed cellulolytic activity up to 11,8 FPU/mL. Regarding to proteolytic activities, six (6) strains showed activity above 10 %, which overpassed results described in the literature. Molecular analyzes based on the identification of 16S rDNA, revealed that all the selected bacterial isolates were affiliated to Bacillus genus. In summary, these results strongly indicate that the isolated bacteria from a hippopotamus can be a potential source of interesting biocatalysts with cellulolytic and proteolytic activities, with relevance for industrial applications.
Highlights
Microorganisms represent the major source of genetic diversity on Earth
São Paulo Zoo Park Foundation (SPZPF) has a UNIT for Organic Composting Production (UOCP) and all of the organic residues, that are generated in the maintenance of the Zoo, including animal carcasses, feed residues and manure are composted under controlled conditions
Qualitative screenings for detection of bacterial cellulolytic activity All the 159 isolated bacteria were screened through qualitative analysis based on the hydrolysis of CMC evidenced by Congo Red dye
Summary
The prestige of microorganisms is due to their high metabolic versatility, which allows the inference about its potential for biotechnological applications, including enzyme production for industrial and environmental uses. In this sense, composting process developed at São Paulo Zoo Park Foundation (SPZPF) can be considered as an important biodiversity source. There are strains or consortia of microorganisms that have demonstrated enzymatic potential to break lignocellulosic materials These compounds are formed by cellulose (40–50 %), hemicellulose (25–35 %) and lignin (15–20 %) (Ragauskas et al 2006; Zhang et al 2006). The activities of cellulases according to their classification are as follow: (a) endoglucanases (EC 3.2.14.4 1,4-β-dglucan-4-glucanohydrolase): promotion of β-1,4 linkage break in amorphous regions, reducing the polymerization degree and producing reduced and non-reduced terminals, exposing microfibrils to other enzymatic attack; (b) cellobiohydrolases (EC 3.2.1.91 1,4-β-d-glucancellobiohydrolases): exoglucanase action in monomers (glucose) or dimers (cellobiose) removing them from terminal portion of the chains; (c) β-glucosidase (EC 3.2.1.21): cellobiose hydrolysis and, in some cases, other small oligosaccharides to glucose; (d) swollenin: action under cellulosic fibers without hydrolytic activity (Aro et al 2005)
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