Assesment of the exploitation potential of various agro-industrial wastes for polygalacturonase production by Aspergillus sojae

FRATEBIANCHI DE LA PARRA, DANTE; CAVALITTO, SEBASTIÁN; ALBANESI, AGUSTÍN; CAVELLO, IVANA

San Martín

Simposio; The Fifth International Symposium on Environmental Biotechnology and Engineering; 2016

Instituto de Investigación e Ingeniería Ambiental (3iA), UNSAM

Pectinases comprise a highlydiverse group of biocatalysts responsible for the enzymatic degradation ofpectic substances, whose function resides in providing integrity to the planttissues. Pectic substances represent together with celluloses the most abundantcomplex polysaccharides from plants. Utilization of biodegradableagro-industrial residues for enzymes production helps to solve environmentalproblems related to its disposal, while allows obtaining value-added productsfrom low-cost substrates. In the present work, the potential of severalagro-industrial by-products to be used as substrate for pectinolytic enzymesproduction by A. sojae was evaluatedunder submerged fermentation.Batch cultures of A. sojae were performed in 250 mlErlenmeyer flasks containing 50 ml of a mineral medium supplemented with 30 g/Lof the respective wastes. Lemon peel, mexican lime peel, orange peel, grapepomace, pear pomace and soybean husk were independently tested for thispurpose. Each substrate was milled with a laboratory mill and sieved through differentmesh sizes; particles retained between meshes 16 and 35 were used for the assays.Cultures were run at 30° C and 120 rpm in an orbital shaker. Samples were takenat different times during the incubation period, centrifuged and thesupernatants assayed for polygalacturonase (PGase) activity determination.All by-products except grapepomace proved to be adequate substrates for acidic PGase production by A. sojae, with maximum activity values obtainedbetween 135 and 180 h of cultivation. The highest PGase production was achievedwith mexican lime peel as substrate (69 U/ml), while utilization of lemon peeland orange peel also showed good results (56 and 61 U/ml, respectively). The pHprofiles along the culture period showed that, unlike cultures with the otherwastes which occurred at acid pH values, those with grape pomace reached pHvalues of approximately 9,5 after 80 h, being most likely the cause of theabsence of PGase activity observed with this substrate. In contrast, culturesperformed with pear pomace reached highly acidic pH values (pH 1.3) after thethird day of cultivation, and consequently PGase activity was comparatively low(3 U/ml). As for soybean husk, it is worth mentioning that even though these cultures displayed intermediate levelsof PGase activity (17 U/ml); huge amounts of this waste are produced inArgentina, which turns soybean husk into an attractive agro-industrial residueand a different alternative for microbial pectinolytic production.