Jaime Moreno-Garcia, Teresa Garcia-Martinez, Severino Zara, Marilena Budroni, Juan Moreno, Juan Carlos Mauricio, Peter Luong, Minami Ogawa, and Linda F. Bisson*
*Department of Viticulture and Enology, University of California, Davis, CA 95616 (lfbisson@ucdavis.edu)

A novel method of yeast immobilization, called biocapsules, has been developed in which yeasts are attached to the hyphae body of the fungus Penicillium chrysogenum (Peinado et al., 2004). Yeast immobilization allows higher cell densities than traditional fermentation methods, yield improvement, reuse of the biocatalyst, etc. Biocapsule immobilization has been used to produce white, sweet, and sparkling wines and in bioethanol production (Peinado et al., 2005; Puig-Pujol et al., 2013; García-Martínez et al., 2015; García-Martínez et al., 2011). In a yeast screening for fungus co-immobilization, flor strains formed the most consistent biocapsules. These yeast naturally form a biofilm on the liquid surface of sherry wines, in which the cell wall Flo11 protein plays an essential role. Loss of FLO11 in a flor strain decreased immobilization five-fold, indicating that flor formation likely influences yeast-fungus co-immobilization. Biofilms form on interphases (solid or liquid) via cell-cell and/or cell-surface attachment. Flocculation occurs in liquid media and refers to the attachment of cells to each other when grown dispersed. Flo11 protein is essential in biofilm formation and also participates in flocculation. To elucidate the influence of biofilm formation versus flocculation on yeast-fungus co-immobilization, 19 biofilm-forming and flocculating yeast strains were identified from a screen in the UCD VEN collection and their ability to flocculate and form biofilm was quantified. Strains displaying different abilities to flocculate or form biofilms were also evaluated for their ability to immobilize with P. chrysogenum. Nine strains showed different patterns of flocculation/biofilm formation, making them interesting candidates for immobilization. These results illuminate parameters that influence yeast-fungus co-immobilization that might lead to improvement of biocapsule consistency and further extend the field of application for this new immobilization system.

Funding Support: Spain’s Ministry of Economy and Competitiveness (MINECO-INIACCAA) and the European Fund of Regional Development (FEDER), Grant No. RTA2011-00020-C02-02). Visiting Researcher Scholarship from the Fulbright Commission in Spain.