Production, concentration and partial characterization of an enzymatic extract produced by an Aspergillus niger mutant in solid state fermentation.

An enzymatic extract from Aspergillus niger 3T5B8 was produced by Solid State Fermentation (SSF) in aerated columns, using wheat bran as substrate. A combination of extracts produced using three different process conditions varying temperature, pH and aeration formed the final extract (Mixture). The Mixture was concentrated by an ultrafiltration process that partially purified and provided an efficient recovery of the enzymatic activities of xylanase (88.89%), polygalacturonase (89.3%), ß-glucosidase (93.15%), protease (98.68%) and carboxymethylcellulase (CMCase) (98.93%). SDS-PAGE analysis showed 15 visible protein bands in the crude and concentrated Mixture with molecular weights ranging from 15.1 to 104.6 kDa. Thin layer chromatography confirmed the effective action of ß-glucosidase and xylanase hydrolysis activities over cellobiose and xylan, respectively. A central composite design (CCD) with two variables and four replicates at the center points was used to determine the optimal temperature and pH for CMCase and ß-glucosidase. The optimal temperature was 78.9 °C and pH 3.8 for CMCase and 52.8 °C and pH 4.8 for ß-glucosidase, respectively.

Structure and functional properties of cellulose acetate films incorporated with glycerol.

Tests were performed with cellulose acetate films (CA) incorporating 5, 10, 20, 30, and 50% (w/v) of glycerol with the purpose of evaluating the possible changes caused by the plasticizer on the functional properties of the packaging. The glass transition temperature (Tg) and relative crystallinity (RC) were are obtained by DSC and XRD, respectively. The results showed that, the presence of glycerol in the films caused increased thickness, water vapor transmission rate (WVTR), and optical properties for most treatments. Moreover, morphological changes were evidenced in scanning electron microscopy (SEM). A reduction of tensile strength (TS) and Young's modulus (YM) was observed only in the concentration of 50% of glycerol. Therefore, the results suggest that there was an interaction between glycerol and cellulose acetate, demonstrating that the film has potential for use as food packaging.