α-l-arabinofuranosidase production byAspergillus nidulans

The effects of some physico-chemical parameters on production of extracellular alpha-L-arabinofuranosidase by Aspergillus nidulans were examined. Highest levels of alpha-L-arabinofuranosidase were generated with cultures grown on 1% (w/v) purified beet pulp arabinan at 30 degrees C and at an initial pH of 7.0. The enzyme was shown to be very sensitive to the action of proteases. Zymogram overlay of a protein profile obtained by SDS-PAGE revealed the occurrence of a band (M(r) 36,000) exhibiting alpha-L-arabinofuranosidase activity. The isoelectric pH of the enzyme lay near 4.3. Temperature and pH optima for the activity of crude alpha-L-arabinofuranosidase preparations were 55 degrees C and 5.5, respectively. Enzyme activity was greatly reduced by thiol reagents such as Hg2+ and p-hydroxymercuribenzoate and showed a Km value of 2.7 mM on p-nitrophenyl alpha-L-arabinofuranoside as substrate.