Abstract
Wickerhamomyces anomalus strain WaF17.12 is a yeast with an antiplasmodial property based on the production of a killer toxin. For its symbiotic association with Anopheles mosquitoes, it has been proposed for the control of malaria. In an applied view, we evaluated the yeast formulation by freeze-drying WaF17.12. The study was carried out by comparing yeast preparations stored at room temperature for different periods, demonstrating that lyophilization is a useful method to obtain a stable product in terms of cell growth reactivation and maintenance of the killer toxin antimicrobial activity. Moreover, cytotoxic assays on human cells were performed, showing no effects on the cell viability and the proinflammatory response. The post-formulation effectiveness of the killer toxin and the safety tests indicate that WaF17.12 is a promising bioreagent able to impair the malaria parasite in vector mosquitoes.
Highlights
Wickerhamomyces anomalus is a ubiquitous ascomycete yeast that is isolated from different sources, such as food, plants and insects [1]
The effect on the growth reactivation and the maintenance of the killer toxin activity after freeze-drying was evaluated, demonstrating that WaF17.12 is a stress-tolerant strain that is transformable into a dried product, ready to use in the field
Analysis of the yeast cultures was performed after 36 h of incubation at optimal conditions for stimulating the secretion of WaF17.12-killer toxins (KTs) [16] (Figure 1)
Summary
Wickerhamomyces anomalus (formerly Pichia anomala and Hansenula anomala) is a ubiquitous ascomycete yeast that is isolated from different sources, such as food, plants and insects [1]. This yeast has gained great attention for its applicability in food biopreservation and potential use in medicine, thanks to its ability to produce killer toxins (KTs) with a wide antimicrobial activity [1]. In-depth studies of the killer yeast effects on humans and the environment as well as tests of the maintenance of the KT-based antimicrobial properties in formulated products are necessary for its further biotechnological applications. For its association as a mutualistic symbiont with insects that transmit diseases to humans and animals, such as mosquitoes and sandy flies, W. anomalus has been proposed for the symbiotic control (SC) of vector-borne diseases (VBDs) [3,4]. Malaria is one of the most troubling VBDs, and the fight against vector mosquitoes is mainly based on insecticides. A possible approach involves the dissemination in vector mosquitoes of inherited symbiotic yeasts that kill the malaria pathogen (Plasmodium) from an infected blood meal, by releasing
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