Harnessing soybean hulls for improved polygalacturonase production by Aspergillus sojae through fine-tuning of ambient pH

FRATEBIANCHI DE LA PARRA, DANTE; ACOSTA, MARINA ALEJANDRA; CAVALITTO, SEBASTIÁN FERNANDO

JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY

JOHN WILEY & SONS LTD

Año: 2018 vol. 93 p. 667 - 674

0268-2575

BACKGROUNDSoybean hulls result from the processing of the bean for producing oil and protein products. This by-product generated massively in America has virtually no commercial value, so substantial effort is being paid into its exploitation for generating value-added goods. This work evaluates soybean hulls as inducer of the production of pectinolytic enzymes, through optimization studies regarding polygalacturonase production by Aspergillus sojae in submerged cultures.RESULTSA 2-fold improvement in polygalacturonase yield was found by varying the initial pH of the culture in a very narrow acid pH range (2.40-2.80). The optimized fermentation process was successfully transferred to stirred-tank bioreactors in terms of volumetric productivity, and final polygalacturonase yields were 42 U/ml and 1.39 U/g soybean hulls, which are among the highest reported with this by-product. Morphological characterization of A. sojae during cultivation showed that the fungus mainly developed in dispersed mycelia at initial pH of 2.40-2.80 whilst, conversely, fungal pellets predominated in cultures performed at initial pH of 5.40.CONCLUSIONHigh enzyme titers are possibly connected to the formation of dispersed mycelia, as well as to acid-induced expression of the respective gene/s. We foresee this data will be helpful regarding the production of fungal pectinases or other acid-induced enzymes.