Utilization of agri-food industry by-products as sustainable substrates for pullulan production by Aureobasidium spp. strains: implications for food packaging sustainability

Pullulan is a microbial exopolysaccharide obtained by fermentation of the yeast like fungus Aureobasidium spp. Pullulan has various applications as food additive in the form of a thickening agents and stabiliser. In the last decade, it has also been used for the formulation of edible coatings and films in food packaging. The production of pullulan by Aureobasidium spp. is strain dependent and is strongly affected by the growth medium and conditions. Due to the high value of pullulan, it is fundamental to find alternative low-cost substrates for its production. The food industry produces large quantities of waste and by-products and the possibility to use these substrates for the pullulan production by Aureobasidium represents an opportunity that need to be explored. In this study, the capability of two different Aureobasidium strains (A. pullulans var.melanogenum DSM 2404 and A. pullulans DSM 3042) to grow and to produce pullulan in four different agri-food by products, was investigated. In particular, the Aureobasidium strains were grown on whey, olive pomace, grape pomace, and molasses. The pullulan production process was optimised taking into account different variables such as temperature, pH, substrate ratio and fermentation time. The results showed that the two tested Aureobasidium strains were able to produce pullulan in all the tested by-products. However, the production rate was strongly affected by the strain and the substrate. Both the strains showed the highest pullulan production on whey followed by olive pomace, grape pomace and molasses. Nonetheless, the strain A. pullulans DSM 3042 showed the highest pullulan rate in all the considered substrates and conditions. In conclusion, the utilisation of food industry by-products as a carbon source for pullulan production by A. pullulans strains is not only a sustainable approach but also has promising implications for the food packaging industry. Pullulan, known for its excellent film-forming properties, offers a biodegradable alternative for food packaging materials that meets the increasing demand for sustainable packaging solutions. However, further studies in order to characterize the quality and purity of the pullulan obtained by the various by-product should be performed.