Abstract
The “alperujo” is a waste from the olive oil industry with great potential for valorization. It has a high organic load, with the presence of valuable compounds such as biophenols and sugars. The use of this waste can be thought of as a biorefinery from which different compounds of high added value can be obtained, whether they are present in the “alperujo” such as biophenols or can be generated from the “alperujo”. Therefore, the production of carotenoids by Rhodotorula mucilaginosa was evaluated using the liquid fraction of ‘alperujo’ (Alperujo Water, AW) or an aqueous extract (AE) of “alperujo” at different concentrations (5, 10, 20 and 30% w/V) as substrates. The AEs had an acidic pH, a total sugar concentration ranging from 1.6 to 7.6 g/L, a polyphenols content from 0.4 to 2.9 g/L and a significant amount of proteins (0.5–3 g/L). AW is similar in composition as 30% AE, but with a higher amount of total sugars. Rh. mucilaginosa was able to grow at the different mediums with consumption of glucose and fructose, a reduction in protein content and alkalinization of the medium. Maximum total carotenoid production (7.3 ± 0.6 mg/L) was achieved at AW, while the specific production was higher when the yeast grew at AW or at 30% AE (0.78 ± 0.06 and 0.73 ± 0.10 mg/g of biomass, respectively). Torulene and torularhodin were the main carotenoids produced. Polyphenol content did not change; thus, it is still possible to recover these compounds after producing carotenoids. These results demonstrate the feasibility of using alperujo-based mediums as cheap substrates to produce torularhodin and torulene and to include this bioprocess as a step in an integral approach for alperujo valorization.
Highlights
Nowadays, olive oil is obtained by two- and threephase centrifugation systems which in most countries replace the traditional pressing
We explore the production of carotenoids, in particular, torulene and torularhodin, by a strain of Rhodotorula mucilaginosa using different medium derived from alperujo as cheap substrates
The composition of olive wastes varies depending on the olive variety, climate conditions, cultivation practices and storage time, we found values were consistent with other reports (Giannoutsou et al 2004; Dermeche et al 2013; Serrano et al 2017)
Summary
Olive oil is obtained by two- and threephase centrifugation systems which in most countries replace the traditional pressing. These systems save water and energy and improve oil recovery; different by-products are generated that need to be appropriately managed (Morillo et al 2009). (2020) 7:52 of some of these valuable compounds like hydroxytyrosol and tyrosol, both recognized potent antioxidants (Rubio-Senent et al 2013; Fernández-Prior et al 2020) Even with these treatments, alperujo may be under-exploited as most lignocellulosic feedstocks (Unrean 2016). This strategy provides the possibility of producing high value-added products such as biopolymers, enzymes and pigments with a concomitant reduction of the organic load (Borroni et al 2017; Moya Ramírez et al 2016; Elisashvili et al 2018; Zerva et al 2017)
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