Fungi from industrial tannins: potential application in biotransformation and bioremediation of tannery wastewaters

Abstract

Tannins are a complex family of polyphenolic compounds, widely distributed in the plant kingdom where they act as growth inhibitors towards many microorganisms including bacteria, yeasts, and fungi. Tannins are one of the major components of tannery wastewaters and may cause serious environmental pollution. In the present study, four different tannins (the hydrolysable chestnut ellagitannin and tara gallotannin and the condensed quebracho and wattle tannins) were characterized from a mycological point of view with the aim of selecting fungal strains capable of growing in the presence of high tannin concentration and thus potentially useful in industrial biotransformations of these compounds or in the bioremediation of tannery wastewaters. A total of 125 isolates of filamentous fungi belonging to 10 species and four genera (Aspergillus, Paecilomyces, Penicillium, and Talaromyces) were isolated from the tannin industrial preparations. Miniaturized biotransformation tests were set up with 10 fungal strains and the high-performance liquid chromatography (HPLC) analysis pointed out a strong activity of all the tested fungi on both chestnut and tara tannins. Two strains (Aspergillus tubingensis MUT 990 and Paecilomyces variotii MUT 1125), tested against a real tannery wastewater, were particularly efficient in chemical oxygen demand (COD) and tannin removal (> 60%), with a detoxification above 74%. These results indicate that these fungi are potentially exploitable in the treatment of tannery wastewaters.

Re-Evaluation of the Taxonomy of Talaromyces minioluteus

“…In our study, we also found that these two species most common in the T. minioluteus-clade. Talaromyces minioluteus and related species have a worldwide distribution, but seem to be more frequently encountered in warmer climates [1,37,38]. Furthermore, these species occur on various substrates (e.g., indoor environment, wall paintings and fruits such as citrus, pear and quince).…”

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“…Tannins have been reported to prevent the development of microorganisms by precipitating microbial protein and making nutritional protein unavailable for them (Ullah et al, 2018) [30,31,32,33] . The growth of many fungi, yeasts, bacteria and viruses was inhibited by tannins (Prigione et al, 2018) [20] .…”

Biotransformation of industrial tannins by filamentous fungi

“…In an established consortium, several enzymatic isoforms from different species may be complementary in the degradation of complex matrices, and mutualistic or antagonistic relationships may ultimately enhance enzymatic production (Ijoma and Tekere 2017). Furthermore, different species showed specific activity dependent on the tannin to be treated (Prigione et al 2018). Likewise some strains are more effective against the Chemical Oxygen Demand (COD) and other on the total phenol content (Perovano et al 2011).…”

“…Lekha and Losane 1997 Ascochyta pisi Lekha and Losane 1997 Ascochyta viciae Lekha and Losane 1997 Aspergillus acidus Prigione et al 2018Aspergillus aculeatus Banerjee et al 2001El-Tanash et al 2011…”