Use of alginate for extending shelf life in a lyophilized yeast-based formulate in controlling green mould disease on citrus fruit under postharvest condition

Tentative to extend shelf-life of lyophilized yeast-based formulations arouses great interest in the phytosanitary drug market. The challenge of this work was to set an simple, innovative and inexpensive system that use alginate for making gummosis gel beads able to preserve for longer time vitality, morphological stability and biological activity of lyophilized-yeast used as biocontrol mean against fruit commodity losses caused by the phytopatogenic fungus Penicillium digitatum, the main causal agent of green mould disease on citrus fruit under postharvest condition. Two lyophilized-yeast strains belonging to Pichia guilliermondii (5A) and Candida oleophila (13L), three Na-alginate doses (1, 2 and 3%), and three storage temperatures (0, 4 and 15 °C) were considered for assessing shelf life of immobilized-yeast into a sodium-alginate matrix. The results show that shelf life of this innovative biological product suitable for controlling citrus fruit green mould can be elongated up to fourteen months under storage temperature of 4 °C using 3% Na-alginate. Gel beads containing both yeast strains showed more than 60% citrus fruit decay inhibition if employed after storage at 4 °C for fourteen months. A positive correlation highly significant between sodium-alginate dose and yeast cells vitality with the citrus fruit decay inhibition was found.