Evaluation of coffee pulp as substrate for polygalacturonase production in solid state fermentation
The purpose of this research is to evaluate the coffee pulp, a by-product of coffee processing, as substrate for polygalacturonase production by solid state fermentation. In addition, it is a way to take advantage of the coffee pulp. Characterization of the coffee pulp revealed a high content of nutrients for fungi growth, such as reducing sugars (5.4% of dry pulp), proteins (9.4% of dry pulp), pectins (20.5% of dry pulp), which are inducers of pectic hydrolases production and source of carbon after degradation, and caffeine (1.4% of dry pulp), among others. The characterization of the cell-wall of coffee pulp revealed, after polysaccharides fractionation, the content in cell-wall pectins (25.5%), hemicelluloses (11.5%) and cellulosic residue (44%). A strain of Aspergillus niger, called van Thiegem, has been selected as a good producer of polygalacturonases (60 U/ml) using the coffee pulp as the growth substrate. During fermentation, reducing sugars, caffeine and phenolic compounds were consumed till almost exhaustion. A partial characterization of the polygalacturonase using high methoxyl pectin as substrate indicates an optimal pH of 4.0 and 45oC as optimal temperature, which are good values for the use of the enzyme in vegetable processing, including coffee processing.
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