Integrated biorefinery for the biosynthesis of carotenoids-derived products from the yeast Rhodosporidium toruloides from residual urban biomasses

Microbial diversity is a plentiful repository for the development of biorefineries based on residual biomasses. In this work we focus on the use of the yeast Rhodosporidium toruloides, known for the ability to consume pentose and hexose sugars, and to withstand several inhibitory compounds that might arise from lignocellulosic biomasses. At the same time, it naturally produces valuable compounds (e.g. carotenoids); nevertheless, its potential is not yet fully exploited. To explore biodiversity in terms of raw material we used the bark and wood of sessile oak and mulberry trees obtained from the maintenance of the Besozza Park (Pioltello, MI). Their lignocellulosic composition can provide both fermentable sugars (released by enzymatic hydrolysis) and lignin moiety, which can be valorised as biopolymer for the production of nanocapsules. The main goal of the project is to maximise the components of the initial biomasses to obtain microbial carotenoids embedded in lignin-derived nanocapsules. The first step of the process involves the hydrolysis of the residual biomasses (mulberry and sessile oak wood and bark) to obtain growth media for the yeast, successfully releasing a sufficient amount of sugars. These data, combined with the growth kinetics of R. toruloides, demonstrate that they are suitable substrates for growth and for carotenoids production too, which were analysed and quantified by flow-injection analysis coupled with mass spectrometry (FIA-MS). The production of β-carotene and torulene is therefore evaluated during time. To fully utilize the waste biomass, adhering to the principles of bioeconomy and circular economy, the residual lignin from enzymatic hydrolysis is used to produce nanocapsules, which can host yeast-derived carotenoids as cargo for several applications. This work provides insights on the valorization of lignocellulosic biomass in terms of both microbial based bioprocesses and material science applications, fostering the collaboration between different fields, as core principle of bioeconomy. This project is funded by the National Biodiversity Future Center (NBFC), a EU funded project aiming to promote sustainable development.