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. 2019 Jul 24;24(15):2697.
doi: 10.3390/molecules24152697.

Formation of Zearalenone Metabolites in Tempeh Fermentation

Antje Borzekowski  1 , Riyan Anggriawan  2 , Maryeni Auliyati  2 , Hans-Jörg Kunte  3 , Matthias Koch  1 , Sascha Rohn  4 , Petr Karlovsky  2 , Ronald Maul  5
Affiliations

Formation of Zearalenone Metabolites in Tempeh Fermentation

Antje Borzekowski et al. Molecules. .

Abstract

Tempeh is a common food in Indonesia, produced by fungal fermentation of soybeans using Rhizopus sp., as well as Aspergillus oryzae, for inoculation. Analogously, for economic reasons, mixtures of maize and soybeans are used for the production of so-called tempeh-like products. For maize, a contamination with the mycoestrogen zearalenone (ZEN) has been frequently reported. ZEN is a mycotoxin which is known to be metabolized by Rhizopus and Aspergillus species. Consequently, this study focused on the ZEN transformation during tempeh fermentation. Five fungal strains of the genera Rhizopus and Aspergillus, isolated from fresh Indonesian tempeh and authentic Indonesian inocula, were utilized for tempeh manufacturing from a maize/soybean mixture (30:70) at laboratory-scale. Furthermore, comparable tempeh-like products obtained from Indonesian markets were analyzed. Results from the HPLC-MS/MS analyses show that ZEN is intensely transformed into its metabolites α-zearalenol (α-ZEL), ZEN-14-sulfate, α-ZEL-sulfate, ZEN-14-glucoside, and ZEN-16-glucoside in tempeh production. α-ZEL, being significantly more toxic than ZEN, was the main metabolite in most of the Rhizopus incubations, while in Aspergillus oryzae fermentations ZEN-14-sulfate was predominantly formed. Additionally, two of the 14 authentic samples were contaminated with ZEN, α-ZEL and ZEN-14-sulfate, and in two further samples, ZEN and α-ZEL, were determined. Consequently, tempeh fermentation of ZEN-contaminated maize/soybean mixture may lead to toxification of the food item by formation of the reductive ZEN metabolite, α-ZEL, under model as well as authentic conditions.

Keywords: Aspergillus oryzae; Rhizopus; food fermentation; modified mycotoxins; zearalenone sulfate; α-zearalenol.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Structures of zearalenone and major zearalenone metabolites.
Figure 2
Figure 2
Tempeh production in laboratory-scale established based on usual Indonesian practice.
Figure 3
Figure 3
Basal contamination of maize raw material with zearalenone (ZEN) and ZEN-14-sulfate (ZEN-14-S).
Figure 4
Figure 4
Content and relative distribution of zearalenone (ZEN), α-zearalenol (α-ZEL), ZEN-14-sulfate (ZEN-14-S), α-ZEL-sulfate (ZEL-S), ZEN-14-glucoside (ZEN-14-G), and ZEN-16-glucoside (ZEN-16-G) in tempeh-like products fermented with the strains Rhizopus microsporus var. oligosporus CSP, Aspergillus oryzae CJBY, Rhizopus oryzae WJBE, Rhizopus microsporus var. oligosporus CJG, Rhizopus microsporus var. chinensis CJBY; for each fungal strain, fermentation was conducted in quadruplicate; each incubation was analyzed twice; sum free includes ZEN and α-ZEL amount; sum conjugates includes amount of the analyzed ZEN and ZEL conjugates.
Figure 5
Figure 5
Sampling map (Java, Indonesia).
See this image and copyright information in PMC

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