Evaluation of orange peel, an industrial waste, for the production of Aspergillus sojae polygalacturonase considering both morphology and rheology effects

Abstract

Orange peel is an agroindustrial waste rich in pectin and known to be an inducer for pectinase production. The use of this low-cost substrate for the production of an industrially important enzyme, polygalacturonase (PG), can be an alternative way to turn this waste into a value-added product, contributing to the reduction of environmental waste disposal problems. Enzyme productions by fungal microorganisms are affected by environmental and nutritional factors, demanding the determination of optimum conditions for maximum enzyme production with the desired fungal morphology and broth rheology. Therefore, complex and additional carbon sources were optimized with respect to PG production by Aspergillus sojae using statistical approaches. Effect of pH, another significant parameter affecting the rheology and morphology of the strain, was investigated in the serial bioreactor system using the optimized medium composition. Highest PG enzyme yield and productivity together with the maximum PG enzyme production (93.48 U/mL) were obtained under uncontrolled pH conditions. Under these conditions, morphologically, pellet sizes exhibited a normal distribution ranging between 0.5-1.0 mm and 1.0-1.5 mm, and rheological measurements revealed that fermentation broths showed non-Newtonian flow. The low pH trend observed during the course of the fermentation was another important positive outcome for industrial fermentations, prone to contamination problems.The Scientific and Technological Research Council of Turkey and the Bundes Ministerium für Bildung und Forschung through the Intensified Cooperation Project of IntenC 107O60

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

“…pH 3, pH 4, pH 5, pH 6), to obtain high enzyme titers. 6,27 In the present study, however, the 2-fold improvement in PG yields accomplished by changing pHi over such a narrow range further shows the importance of fine-tuning initial pH conditions in order to enhance PG production.…”

“…From a bioprocess point of view, studies dealing with PG production by A. sojae utilizing ground orange peels in submerged fermentation have demonstrated the advantage of cultivating the fungus under uncontrolled pH conditions from above any other controlled pH value (e.g. pH 3, pH 4, pH 5, pH 6), to obtain high enzyme titers . In the present study, however, the 2‐fold improvement in PG yields accomplished by changing pHi over such a narrow range further shows the importance of fine‐tuning initial pH conditions in order to enhance PG production.…”

“…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.…”

<b>Use of agro-industrial wastes as substrates for α-amylase production by endophytic fungi isolated from <i>Piper hispidum</i> Sw

“…In present-day Biotechnology, the demand for new and more potent sources of industrial enzymes is ever growing (Zaferanloo, Virkar, Mahon, & Palombo, 2013); therefore, the enzyme production by fungi represents a crucial sector of the fermentation industry (Göğüş et al, 2014). Brazilian researchers should further explore the potential of endophytes as enzymatic sources, as the country has a continental area with hundreds of plant species that harbor a highly diverse endophytic assemblage (Orlandelli et al, 2015).…”