Utilization of orange peel, a food industrial waste, in the production of exo-polygalacturonase by pellet forming Aspergillus sojae

Abstract

The production of exo-polygalacturonase (exo-PG) from orange peel (OP), a food industrial waste, using Aspergillus sojae was studied in submerged culture. A simple, low-cost, industrially significant medium formulation, composed of only OP and (NH 4 ) 2 SO 4 (AS) was developed. At an inoculum size of 2.8 9 10 3 spores/mL, growth was in the form of pellets, which provided better mixing of the culture broth and higher exo-PG activity. These pellets were successfully used as an inoculum for bioreactors and 173.0 U/mL exo-PG was produced. Fed-batch cultivation further enhanced the exo-PG activity to 244.0 U/mL in 127.5 h. The final morphology in the form of pellets is significant to industrial fermentation easing the subsequent downstream processing. Furthermore, the low pH trend obtained during this fermentation serves an advantage to fungal fermentations prone to contamination problems. As a result, an economical exo-PG production process was defined utilizing a food industrial byproduct and producing high amount of enzyme.

Control of agitation rate and aeration for enhanced polygalacturonase production in submerged fermentation by Aspergillus sojae using agro‐industrial wastes

“…Comparing PGase activity achieved in the present study with the values reported in the literature in submerged fermentations, yields were clearly improved with respect to those previously obtained with A. sojae . PGase activity obtained when A. sojae was grown in shake flasks with maltrin as the main CES was nearly 17 U/ml .…”

“…In another study, a pre‐optimized culture medium containing orange peel and sugar beet syrup was tested in a 5‐L bioreactor, resulting 145 U/ml of PGase activity . Fed‐batch cultivation of A. sojae in 5‐L bioreactors using orange peel as CES further enhanced the PGase activity levels to 244 U/ml . Hence, utilization of apricot pomace combined with orange peel in submerged cultures allowed at least a 1.5‐fold increase in PGase activity from A. sojae with respect to previous works.…”

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

“…The inflection point in the DOT trend, consistent with the above explanation, has been reported previously for A. sojae growing in submerged cultures utilizing other by-products such as orange peels and apricot pomace. 7,8 In this type of submerged fermentation with filamentous fungi where powdered, vegetable raw material is used as carbon source, oxygen limitation has proved to be a factor that affects enzyme yields significantly. For instance, by preventing the DOT from dropping below 20% a 1.5-fold improvement in PG yields was achieved.…”

“…Currently, industrial production of pectinases is mainly performed by A. niger , partly due to the high titers obtained, although great efficiency in the production of extracellular enzymes is not a hallmark restricted to this species. In fact, within recent years several studies have been performed that report the effective production of PGs by A. sojae …”

“…The rationale behind this approach lies in the relatively higher content of cellulose and hemicellulose compared with pectin in soybean hulls, which is in turn apparent due to the nature of the by‐product. Nevertheless, since A. sojae was demonstrated to be an outstanding producer of pectinolytic activity employing agricultural residues rich in pectic substances such as orange peel and apricot pomace, a pectinases production study linking this efficient microbial strain and soybean hulls as both substrate and inducer can certainly be of interest. It is worth mentioning that soybean hulls are produced mainly in the Pampean region in Argentina, which is also the place where this investigation was carried out in an effort to valorize the residue.…”