Bioproduction of α-terpineol and R-(+)-limonene derivatives by terpene-tolerant ascomycete fungus as a potential contribution to the citrus value chain

Abstract

Aims: The aims of this article were to select fungal species with high tolerance and high growth rate in mediums supplemented with limonene and citrus essential oils (CEOs), and to test the bioconversion capability of the chosen isolates for the bioproduction of aroma compounds. Methods and Results: Based on the use of predictive mycology, 21 of 29 isolates were selected after assaying R-(+)-limonene and CEO tolerance (10 g l−1). With a dendrogram divisive coefficient of 0·937, the subcluster two with isolates Aspergillus niger LBM 055, Penicillium sp. LBM 150, Penicillium sp. LBM 151 and Penicillium sp. LBM 154 gathered the highest tolerance and mycelia growth speed. Ultrastructural analysis indicated that culture media containing limonene had no visible toxic activity that could promote morphological changes in the fungal cell wall. The biomass of A. niger LBM055 was distinctive in liquid media supplemented with R-(+)-limonene (0·57 ± 0·07 g) and it was selected to prove bioconversion capacity, under static and agitated conditions, and converted up to 98% of limonene, yielding a wide variety of products that were quantified by GC-FID. It was obtained at molecular weights less than limonene (64–100%), between limonene and α-terpineol (12–72%) and greater than α-terpineol (2–48%). Conclusions: Aspergillus niger LBM 055, Penicillium sp. LBM 150, Penicillium sp. LBM 151 and Penicillium sp. LBM 154 showed to the highest tolerance and growth rate in mediums supplemented with R-(+)-limonene and orange and lemon essential oils. Particularly, A. niger LBM055, showed limonene bioconversion capability and produced different molecular weights compounds such us α-terpineol. Significance and Impact of the Study: Different bioproducts can be obtained by changing operative condition with the same fungus, and this bioprocess aspect is a significant approach to be adopted on industrial scale leading to the creation of new natural flavours and fragrance compositions.