Download dead-end filtration of disrupted saccharomyces cerevisiae yeast

DEAD-END FILTRATION OF DISRUPTED
SACCHAROMYCES CEREVISIAE YEAST SUSPENSIONS
LOGINOV M. (1,2), LARUE O. (2), LEBOVKA N. (1,2), SHYNKARYK M. (1,2),
NONUS M. (2), LANOISELLE J.-L. (2), VOROBIEV E. (2)
(1)
Institute of Biocolloidal Chemistry named after F.D. Ovcharenko, NAS of Ukraine,
42, blvr. Vernadskogo, Kyiv 03142, Ukraine
(2)
Unite Transformations Integrees de la Matiere Renouveable,
Universite de Technologie de Compiegne, Centre de Recherche de Royallieu,
B.P. 20529-60205 Compiegne Cedex, France
(1)
[email protected]
(2)
[email protected]
Abstract
The interior of the yeast cells (S. cerevisiae) is a rich source of bio-products (proteins,
cytoplasmic enzymes, polysaccharides, etc.) valuable for different applications in
biotechnology, brewing and food industry. Different steps are commonly present in extraction
processes, including techniques for cell disruption, solid liquid separation and final
purification of protein extracts from cells, cell debris and other insoluble particles. The
mechanical high-pressure homogenisation (HPH) methods are more appropriate for high
recovery of interior bio-products, but they have many instrumental restrictions and final
products require thorough purification from cell debris.
In this study, the efficiency of solid-liquid separation of disrupted yeast cells (S.
cerevisiae) suspension by dead-end filtration was investigated. Mechanical (HPH) and
electrically-assisted (high voltage electric discharges, HVED) techniques were applied for
disintegration of yeasts. In HPH technique Nh (1-20) successive passes at fixed homogenizing
pressure within 500 to 1000 bar were applied. In HVED technique Nd (1-450) successive
discharge pulses at 40 kV/cm fixed electric field were used. The efficiency of release of the
intracellular components was characterized by conductivity disintegration index Z and
absorbance spectra. Disintegration techniques involve a reorganisation of yeast cells. The size
distribution of yeast aggregates was controlled by analysis of the microscopic images and
using the laser diffraction instrument. The filtration experiments were done in a dead-end
membrane filtration unit connected to a pressure-regulated air (p=1 bar). The membrane
nominal pore size was 2.5 m. In some experiments, the aggregation of yeast was regulated
by addition of cationic flocculant (poly diallyldimethylammonium chloride).
The study of filtration efficiency revealed complex dependencies on techniques of
disintegration, value of Z and particle size distribution. At the initial (fast) step of filtration,
the increase of Z resulted in increased output for HPH method and decreased output for the
HVED method. At the second step of filtration, the permeate flux declined with time and with
damage degree Z for both HPH and HVED techniques due to lower filter-cake permeability
and membrane fouling. Addition of a flocculant promoted formation of flocks and
accelerated filtration but reduced concentration of bio-products in filtrate. The most effective
extraction and solid-liquid separation at the fast step of filtration were observed for HPH
disruption technique and high damage degree Z = 0.99, which allowed the highest recovery
and maximal output of bio-products in filtrate.
Keywords: Yeasts; Filtration; Disruption; High Pressure Homogenisation; High
Voltage Electric Discharge