Molecular and physiological characterization of Pichia anomala WRL-076 for safety assessment

Abstract: Yeast species have been researched for the past twenty years as potential biocontrol agents. The yeast Pichia anomala is a species that has been isolated from many different environments. Several strains have been demonstrated to be effective for both pre- and post-harvest control of fungal pathogens. P. anomala WRL-076 showed good antagonistic activity against Aspergillus flavus and was field-tested in California pistachio orchards. A few strains of P. anomala were reported to cause infection in immune suppressed individuals and newborn babies in medical facilities. A safety assessment of WRL-076 is essential for its application as a biocontrol agent and is required for EPA registration in United States. The ribosomal IGS of P. anomala strains were sequenced and the data suggest that it is possible to differentiate the beneficial P. anomala strains from clinical pathogenic ones. Growth temperature studies showed that WRL-076 and P. anomala isolates from plants did not grow at 37 or 40 °C in nutrient broth. This suggests the yeast will not survive in humans and animals with body temperatures of 37 °C and above.