Enhancing or Inhibitory Effect of Fruit or Vegetable Bioactive Compound on Aspergillus niger and A. oryzae

Abstract

Fruit and vegetable processing wastes are global challenges but also suitable sources with a variety of nutrients for different fermentative products using bacteria, yeast or fungi. The interaction of microorganisms with bioactive compounds in fruit waste can have inhibitory or enhancing effect on microbial growth. In this study, the antimicrobial effect of 10 bioactive compounds, including octanol, ellagic acid, (−)-epicatechin, quercetin, betanin, ascorbic acid, limonene, hexanal, car-3-ene, and myrcene in the range of 0–240 mg/L on filamentous fungi Aspergillus oryzae and Aspergillus niger were investigated. These fungi were both found to be resistant to all compounds except octanol, which can be used as a natural antifungal agent, specifically against A. oryzae and A. niger contamination. On the contrary, polyphenols (quercetin and ellagic acid), ascorbic acid, and hexanal enhanced A. niger biomass yield 28%, 7.8%, 16%, and 6%, respectively. Furthermore, 240 mg/L car-3-ene was found to increase A. oryzae biomass yield 8%, while a 9% decrease was observed at lower concentration, 24 mg/L. Similarly, up to 17% decrease of biomass yield was observed from betanin and myrcene. The resistant nature of the fungi against FPW bioactive compounds shows the potential of these fungi for further application in waste valorization.

Inhibitory and Stimulatory Effects of Fruit Bioactive Compounds on Edible Filamentous Fungi: Potential for Innovative Food Applications

“…Similarly, in previous studies, Aspergillus spp. and Candida glabrata were shown to be resistant to ellagic acid [29,40]. One reason for our results contradicting previous work reporting an antifungal effect may be related to the differences in the cell wall composition of different fungal species [41].…”

“…Ten bioactive compounds (D-limonene, myrcene, car-3-ene, quercetin, epicatechin, ellagic acid, octanol, betanin, hexanal, and L-ascorbic acid) were examined individually at three different concentrations (2.4, 24, and 240 mg/L). For each compound, a stock solution was prepared according to the procedure described by Bulkan et al [29]. For those compounds with low solubility in milli-Q ® water (D-limonene, quercetin, and epicatechin), ethanol was used as the solvent.…”

“…The preparation of the cultivation media containing 2.4, 24, and 240 mg/L bioactive compounds was carried out in a similar fashion to the compounds with ethanol solvent. The stock solutions of the remaining compounds were prepared using milli-Q ® water, except for ellagic acid, which was dissolved in 1 M NaOH solution [29].…”

“…It is commonly found in fruits and vegetables, such as beetroot, pitahaya, tubers, etc. [29]. Unlike R. oligosporus, some microorganisms are susceptible to betanin due to its antimicrobial properties.…”

“…There are a limited number of studies about the valorization of fruit/FPRs, e.g., mango waste, apple pomace, and grape residuals from wineries, by filamentous fungi [26][27][28]. Furthermore, studies that focus on inhibiting or enhancing effect of bioactive compounds from fruit/FPRs are scarce in the literature; however, one study reported that octanol showed an antifungal effect [29]. To be able to implement efficient fermentation processes, knowledge about the effects of potentially inhibitory compounds in nutrient media on filamentous fungi is necessary.…”