ARS | Publication request: Cold Shock During Liquid Production Increases Storage Shelf-Life of Cryptococcus Nodaensis Oh 182.9 after Air Drying

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 2005
Publication Date: January 24, 2006
Citation: Zhang, S., Schisler, D.A., Jackson, M.A., Boehm, M.J., Slininger, P.J., Liu, Z. 2006. Cold shock during liquid production increases storage shelf-life of Cryptococcus nodaensis OH 182.9 after air drying. Biocontrol Science and Technology. 16(3):281-293.

Interpretive Summary: Fusarium head blight (FHB) or scab of wheat is a devastating disease worldwide. A yeast we discovered named Cryptococcus nodaensis OH 182.9 effectively reduced scab disease in greenhouse and field tests when fresh cells or frozen concentrates were used. To be of practical use, OH 182.9 must be formulated as a dry product in order to be easily stored, distributed and applied in the agricultural marketplace. This requires the development of convenient, economical methods for producing stable, effective biomass. A particular concern in this process is to stabilize cells such that cells remain alive and effective through many months of storage. Air-drying is a convenient and economical drying method for addressing this concern. We investigated how temperature shock during liquid production of OH 182.9 affects cell survival in an inert carrier (diatomaceous earth (DE)) after air-drying. We discovered that growing cells of OH 182.9 at 25ºC for 20 hours and then changing the temperature to 10 or 15ºC for 28 h enhanced the stability of the dried, DE-formulated OH 182.9 product made from these cells. In greenhouse tests, air-dried OH 182.9 cell products from cold shock treatments maintained an acceptable level of biocontrol. This discovery is critical in the process of developing a stable, effective biocontrol product which would benefit wheat farmers by providing an environmentally friendly tool for wheat scab management.

Technical Abstract: Fermentation, formulation, and drying studies are necessary and important in order to simplify transportation, storage, and application of biocontrol agents. Air-drying is a convenient and economical drying method for developing microbial products. Experiments were designed to determine the effect of temperature shock during liquid cultivation on cell survival of a Fusarium head blight biocontrol agent Cryptococcus nodaensis OH 182.9 after air-drying. OH 182.9 cultures were grown at various temperatures in semidefined complete liquid media, with cultures grown at 25 deg C for 48 h serving as the standard control culture condition. Harvested cultures were mixed with 10% diatomaceous earth (DE), vacuum filtered, air dried for 20 h at 60-70% RH, and stored at 4 deg C. In general, cells grown at 25 deg C for 20 h followed by cultivation at 15 deg C for 28 h survived air-drying better than control cells. The survival of cells subjected to heat shock at 31 deg C generally did not differ from control cells regardless of whether heat shock was applied at the late exponential or early stationary stage of growth. In another experiment designed to optimize the effect of cold temperatures during cultivation on subsequent survival of air-dried cells in DE at 4 deg C and room temperature (25 deg C), prolonged (28 h) cold shock at 10 and 15 deg C after incubation at 25 deg C for 20 h enhanced the storage stability (shelf-life) of a DE-formulated OH 182.9 product. In greenhouse tests, air-dried cells of OH 182.9 in DE stored for 6 weeks at 4 deg C maintained a higher biocontrol efficacy than those cells stored for 6 weeks at 25 deg C.