Abstract
The use of residues in industrial processing is expanding due to their low cost and abundant availability. Coconut shell is generated in large amounts in tropical areas due to the fruit processing and the coconut water consumption. In the present work, a new microbial strain was isolated from the coconut shell powder, molecularly identified as Melanoporia sp. CCT 7736 and applied for cellulase production in solid-state fermentation using the green coconut shell powder as substrate. The complete production process was optimized. Fermentation time was only 24 h, and the enzyme produced presented maximal activity at neutral pH (6.5) and 60 °C. The maximal enzyme activity after extraction optimization was 7.5 IU/gds (international units of enzyme activity per gram of dry solid). For the enzyme extraction, the rotation velocity, the extraction time, the temperature, and the solvent volume (buffer) were optimized using response surface methodology (RSM). The best results for the enzyme extraction were obtained at 250 rpm (orbital shaker) at 30 °C using 13.79 mL of a sodium acetate buffer (200 mM) at pH 6.5 after 10 min. Delignification pretreatment was not necessary since this fungus strain was able to degrade the lignin. To the best of our knowledge, this work is the first report of cellulase production by Melanoporia sp. CCT 7736. Good results were obtained without the need for expensive pretreatment usually applied to lignocellulosic residues because the strain was isolated from coconut shell powder, and it is well adapted to this kind of substrate. The enzyme presented maximum activity at neutral pH instead of acidic pH as reported for the majority of industrial cellulases. The use of lignified coconut shell and the optimal pH at neutral values are the main advantages of the enzyme produced by Melanoporia sp. CCT 7736. In addition, the enzyme showed good stability during storage even at the crude broth and without any cryoprotection.
Highlights
The use of residues in industrial processing is expanding due to their low cost and abundant availability
CCT 7736 According to the results presented in Table 1, cellulase production decreased with the increasing amount of coconut shell powder, and the maximum enzyme production by Melanoporia sp
The results showed a peak at 24 h and a reduction in that enzyme activity after 24-h fermentation can be attributed to lack of nutrients necessary for the metabolism of Melanoporia sp
Summary
The use of residues in industrial processing is expanding due to their low cost and abundant availability. The agricultural residues and their disposal are a concern due to the exponential increase in food industry. These residues are usually shells, seeds, peels, bagasse and other materials that. Lignocellulose biomass, found in several agriculture residues, is the most abundant renewable resource in the word. This material has been considered for do Rêgo de Oliveira et al Bioresour. Cellulose is the most abundant polymer in nature and represents 50 % of the natural biomass (Wang et al 2012). Cellulosic materials are not directly fermentable, and a hydrolysis step is necessary to obtain simple sugars that can be metabolized by microorganisms (Singh et al 2010)
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