Halotolerant bacteria in the São Paulo Zoo composting process and their hydrolases and bioproducts

Halophilic microorganisms are able to grow in the presence of salt and are also excellent source of enzymes and biotechnological products, such as exopolysaccharides (EPSs) and polyhydroxyalkanoates (PHAs). Salt-tolerant bacteria were screened in the Organic Composting Production Unit (OCPU) of São Paulo Zoological Park Foundation, which processes 4 ton/day of organic residues including plant matter from the Atlantic Rain Forest, animal manure and carcasses and mud from water treatment. Among the screened microorganisms, eight halotolerant bacteria grew at NaCl concentrations up to 4 M. These cultures were classified based on phylogenetic characteristics and comparative partial 16S rRNA gene sequence analysis as belonging to the genera Staphylococcus, Bacillus and Brevibacterium. The results of this study describe the ability of these halotolerant bacteria to produce some classes of hydrolases, namely, lipases, proteases, amylases and cellulases, and biopolymers. The strain characterized as of Brevibacterium avium presented cellulase and amylase activities up to 4 M NaCl and also produced EPSs and PHAs. These results indicate the biotechnological potential of certain microorganisms recovered from the composting process, including halotolerant species, which have the ability to produce enzymes and biopolymers, offering new perspectives for environmental and industrial applications.

Fermentation and recovery of L-glutamic acid from cassava starch hydrolysate by ion-exchange resin column

Investigators were carried out with the aim of producing L-glutamic acid from Brevibacterium sp. by utilizing a locally available starchy substrate, cassava (Manihot esculenta Crantz). Initial studies were carried out in skate flasks, which showed that even though the yield was high with 85-90 DE (Dextrose Equivalent value), the maximum conversion yield (-34 per cent) was obtained by using only partially digested starch hydrolysate, i.e. 45-50 DE. Fermentations were carried out in batch mode in a 5 L fermenter, using suitably diluted cassava starch hydrolysate, using a 85-90 DE value hydrolysate. Media supplemented with nutrients resulted in an accumulation of 21 g/L glutamic acid with a fairly high (66,3 per cent) conversation yield of glucose to glutamic acid (based on glucose consumed and on 81,74 per cent theoretical conversion rate). The bioreactor conditions most conductive for maximum production were pH 7.5, temperature 30§C and an agitation of 180 rpm. When fermentation was conducted in fed-batch mode by keeping the residual reducing sugar concentration at 5(per cent) w/v, 25,0 g/L of glutamate was obtained after 40 h fermentation (16 per cent more the batch mode). Chromatographic separation by ion-exchange resin was used for the recovery and purification of glutamic acid. It was further crystallized and separated by making use of its low solubility at the isoelectric point (pH 3.2).