Some factors affecting efficiency of the ultrasound-aided enzymatic hydrolysis of cotton cellulose.

The efficiency of the enzymatic hydrolysis of cellulose with low frequency ultrasound (horn-type reactor) was investigated and characterized by the concentration of reducing sugars liberated. Small squares of bleached cotton fabric were used for comparing the efficiency of different agitation methods (i.e. magnetic stirring, horizontal and vertical mechanical agitation) and ultrasound. At the same enzyme dosage and substrate level, sonication at 40, 60 and 80% amplitudes (Idiss: 16.2, 32.2 and 43.4W/cm2, respectively) intensified the hydrolysis over the most efficient mechanical agitation (i.e. magnetic stirring) alone by 15%, 24% and 54%, respectively. For mapping the ultrasonicated field, fabric layers positioned perpendicularly to the ultrasonic probe at different distances were hydrolysed. The optimal operating conditions were reached at 60% amplitude and 9mm The yield depended mainly on important factors such as amplitude, the presence of a reflector, distance from horn and form of substrate.

Ultrasound-assisted extraction and characterization of hydrolytic and oxidative enzymes produced by solid state fermentation.

Ligninolytic and hydrolytic enzymes were produced with six selected fungi on flax substrate by solid state fermentation (SSF). The extracellular enzyme production of the organisms in two SSF media was evaluated by measuring the soluble protein concentration and the filter paper, endoxylanase, 1,4-ß-d-glucosidase, 1,4-ß-d-endoglucanase, polygalacturonase, lignin peroxidase, manganese peroxidase and laccase activities of the clear culture solutions produced by conventional extraction from the SSF materials. The SSF material of the best enzyme producer (Trichoderma virens TUB F-498) was further investigated to enhance the enzyme recovery by low frequency ultrasound treatment. Performance of both the original and ultrasound macerated crude enzyme mixtures was evaluated in degradation of the colored lignin-containing and waxy materials of raw linen fabric. Results proved that sonication (at 40%, 60% and 80% amplitudes, for 60min) did not result in reduction in the filter paper, lignin peroxidase and laccase activities of the crude enzyme solution, but has a significant positive effect on the efficiency of enzyme extraction from the SSF material. Depending on the parameters of sonication, the enzyme activities in the extracts obtained can be increased up to 129-413% of the original activities measured in the control extracts recovered by a common magnetic stirrer. Sonication also has an effect on both the enzymatic removal of the lignin-containing color materials and hydrophobic surface layer from the raw linen.

The effect of low-frequency ultrasound on the activity and efficiency of a commercial cellulase enzyme.

A commercial acidic cellulase enzyme complex was chosen in order to gain detailed information about the effect of low-frequency ultrasound (horn at 40 kHz) on the enzyme activity. The performance of the enzyme under sonication was also evaluated in a cellulose-cellulase model reaction. The filter paper activity of the enzyme and the yield of the enzyme catalysed hydrolysis were determined as a function of the parameters of the sonicated environment (treatment time, amplitude, with and without a reflector) and compared with the data measured in a non-sonicated bath. Depending on the parameters of the sonication, the enzyme is susceptible to ultrasound and its activity can significantly decrease. Despite the serious reduction of the enzyme activity, the outcome of the enzyme catalysed hydrolysis was always positive, implying that the advantageous effects of sonication impressed on the heterogeneous enzyme reaction always overcome the undesirable enzyme modifying effect of ultrasound.