Use of Mesophilic Fungal Amylases Produced by Solid-state Fermentation in the Cold Hydrolysis of Raw Babassu Cake Starch

Abstract

Amylases constitute one of the most important groups of industrial enzymes, presenting several applications, such as in the food, textile, and ethanol manufacturing. In this work, a starchy residue from the Brazilian agroindustry, namely babassu cake, was used for the production of amylases by solid-state fermentation and for obtaining sugar hydrolysates, which can be used as building blocks for future bioconversions. Eight filamentous fungi from the genera Aspergillus and Penicillium were screened. Regarding amylase production, A. awamori strains showed well-balanced endoamylase and exoamylase activities, while A. wentii produced an amylolytic complex much richer in the endo-acting enzymes. Simultaneous liquefaction and saccharification using the crude enzyme extracts from the four most promising fungal strains was then investigated applying DOE techniques. The highest total reducing sugar content (24.70 g L(-1)) was obtained by the crude extract from A. awamori IOC-3914, corresponding to a hydrolysis yield of 52% of total starch in the cake, while A. awamori IOC-3915 produced the most appropriate extract in terms of glucose release (maximum of 5.52 g L(-1)). Multivariate analysis of the DOE studies indicated that these extracts showed their best performance at 50-57 degrees C under acid conditions (pH 3.6-4.5), but were also able to act satisfactorily under milder conditions (36 degrees C and pH 5.0), when TRS and glucose released were about 65% of the maximum values obtained. These data confirm the high potential of the enzyme extracts under study for cold hydrolysis of starch.