BACKGROUND: Six different wine yeast strains (G1, X4, X5, P29, QA23, Uvaferm BC) were co-immobilized in a natural, spontaneous way with Penicillium chrysogenum under special conditions without the need for an external support or chemical binder and provided six different yeast biocapsules. The purpose was to characterize and evaluate the biocapsules obtained in terms of yeast cell viability, ethanol production and reusability to assess their suitability for ethanol production and the development of industrially competitive alternative wine and beer production methods. RESULTS: Biocapsule size was found to decrease and quantity to increase with increasing shaking rate during the immobilization process. The fermentations were realized in YPD medium containing 18% (w/v) glucose with repeated fermentations reaching 10% (v/v) ethanol. X4 and Uvaferm BC biocapsules afforded at least seven uses with no significant decrease in ethanol production; P29 and QA23 biocapsules five times; and G1 and X5 three times each. Seemingly, ethanol production was directly related to the viability of yeast cells in the immobilizate under defined assay conditions. CONCLUSIONS: X4 and Uvaferm BC may be the most suitable yeast strains for autoimmobilization on P. chrysogenum with a view to their use in alcoholic fermentation processes. (C) 2011 Society of Chemical Industry