Supervisors info:
Καραγκούνη Αμαλία Καθηγήτρια (Επιβλέπουσα), Χατζηνικολάου Δημήτριος Επικ. Καθηγητής, Γκόνου-Ζάγκου Ζαχαρούλα Λέκτορας
Summary:
The wine of Santorini is incredibly interesting when it is compared to the
normal practices and ideas of viticulture. Taking under consideration the above
mentioned it was studied: a) the biodiversity of yeast and bacteria flora found
in spontaneous vinification (in a laboratory bioreactor) and b) the sequencing
and dominance of yeast and bacteria species during spontaneous fermentation of
must obtained from the variety “Asyrtico”.
The samples (wine 2009, must 2010, spontaneous fermentation of must 2011)
derived from the Greek winery of Gavalas from Megalochori of Santorini. The
treatment of samples included standard cultivation methods on selective and
diagnostic media along with the development of culture – independent techniques
such as: BOX – PCR and 16S PCR for the classification and identification of
bacteria and b) ITS PCR for the classification and identification of yeasts
strains. Totally, 1040 yeasts strains and 374 bacterial strains were isolated.
A comparative study of their populations demostrated that yeasts dominated in
all stages of fermentation as the conditions did not favor the growth of
bacteria (deficiency of nutrients, increased volume of ethanol, prevalence of
anaerobic conditions). In addition, qualitative and quantitative determination
of isolated yeasts and bacteria in all studied cases revealed that their
succession and dominance among the three samples was in good agreement, instead
of the fact that the three samples were of different time of selection
(different crop year). The isolated bacterial strains assigned to the species:
Paenibacillus sp., Kozakia baliensis, Bacillus amyloliquefaciens, Bacillus
licheniformis, Gluconobacter oxydans and Bacillus pumilus, while the isolated
yeasts assigned to the species: Saccharomyces cerevisiae YJM789,
Zygosaccharomyces rouxii, Debaryomyces carsonii, Candida cantarellii and
Saccharomyces cerevisiae ΜΑ09-ΑΝ.
Finally, the isolated bacteria and yeasts were further investigated for bearing
specific characteristics, crucial for the wine industry. Indeed, the last
decades, international competition within the wine market and consumer demands
for newer styles of wines are providing new challenges for innovation in wine
fermentation, such as the isolation of new strains (bacteria or yeasts) with
specific properties, which could be used as starter cultures for performing
wines with the desirable organoleptic characteristics. The criteria for
selecting wine yeasts were ethanol and glucose tolerance and the diminished
production of the gas H2S. Saccharomyces cerevisiae seemed to be the most
appropriate strain from the total of isolated yeasts. On the other hand,
isolated bacteria were screened for tannase activity and the ability of
degrading L – arginine. The results demonstrated that only strains of Bacillus
licheniformis and Bacillus amyloliquefaciens were of biotechnological interest
as they presented tanase activity. However, the fact that they degradated
arginine is of practical significance in wine production as they may be
producers of the carcinogen carbamidio. Hence, a further investigation is
required.
Keywords:
Muste, Wine, Alcoholic Fermentasion, Bacteria, Weast
