Influence of culture conditions on mycelial structure and polygalacturonase synthesis of Aspergillus niger

Abstract

Biosynthesis of polygalacturonase (PG) by A. niger strain R 1/214 correlates with the morphology of mycelium in submerged culture. The mean specific PG-synthesis (PG-U.g-1.h-1) increases with the degree of compactness of mycelium. PG-production can be optimized by a precise adjustment of the culture conditions after direct spore inoculation (diffuse mycelium) but the high synthesis as by compact mycelium is never obtained. Different reasons for the higher enzyme production by the pellet mycelium are discussed. PG-synthesis is assumed to be strictly connected with a limitation of nutrient and oxygen supply.

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

“…4). However, it should not be overlooked that enhancement of PG production in pellet form can be partly a result of altered cellular metabolism and enzyme secretion due to limitations in oxygen and nutrient supply and in removal of metabolic products [42].…”

“…In another study, where agro-based products were utilized for exo-PG production by A. sojae M5/6, the inoculum size of 4 9 10 5 spores/mL resulted in mycelial clumps and viscous culture broths in the presence of all substrates [8]. Hermersdörfer et al [42] observed increased PG synthesis by A. niger in a synthetic medium when it grew as a compact mycelia, which was defined as a large ball with a diameter of 40 mm. The PG activity was considerably lower when the growth was in the form of either diffuse mycelia or pellets of 2-10 mm in diameter [42].…”

“…Hermersdörfer et al [42] observed increased PG synthesis by A. niger in a synthetic medium when it grew as a compact mycelia, which was defined as a large ball with a diameter of 40 mm. The PG activity was considerably lower when the growth was in the form of either diffuse mycelia or pellets of 2-10 mm in diameter [42]. A similar trend was observed for R. oryzae where low inoculum size induced compact large mycelial mass and high lactate production, whereas the fungus formed dispersed mycelia and produced low lactate but high ethanol at high inoculum sizes [39].…”

Influence of metal ions on pellet morphology and polygalacturonase synthesis by Aspergillus niger 3T5B8

“…Sucrose 24.0, (NH4)2SO4 5.0, MgSO4.7H2O 0. were added to the fermentation medium, based on the values proposed in the literature for citric acid or pectinolytic enzymes production (1,12,17). Table 1 shows the levels adopted for this study.…”

“…The relationship between the fungi morphology and the enzyme production in submerged fermentation has also not been widely reported. In shake flask fermentation, the growth of diffuse and compact mycelia by A. niger strains for polygalacturonase synthesis was studied by Hermersdörfer et al (12). They found a direct correlation between the compactness of the pellet and the polygalacturonase synthesis, but despite having used trace metals as micronutrients, the authors excluded reference to them in their final conclusions.…”