Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or...
Patent
1997-04-22
1999-09-21
Ketter, James
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
435 6, 435 691, 435 911, 435 712, 4352521, 4353201, 424 9321, 424 9461, 536 232, 536 237, 536 241, C12Q 100, C12N 100, A01N 6300, C07H 2104
Patent
active
059552581
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION AND PRIOR ART
The invention relates to a process for the lysis of a culture of lactic acid bacteria, or a product containing such culture, by means of a lysin e.g. in producing a fermented food product, e.g. in cheese-making. Such a process is known from WO 90/00599 (AGRICULTURAL & FOOD RESEARCH COUNCIL (AFRC), M. J. Gasson, published Jan. 25, 1990, ref. 1). According to that patent specification the lysin from a Lactococcus (preferably prolate-headed) bacteriophage was used to lyse bacterial starter cultures during cheese-making. Exemplified was the lysin of the bacteriophage .phi.vML3 of Lactococcus lactis ML3. In particular, the lysin can be added to a cheese product or a cheese precursor mixture, e.g. after whey removal, milling and salting. However, this solution has the disadvantage that thorough mixing of the contents of the lysed cells with the cheese product is not easily obtained. Another disadvantage is that the lysin was produced by Escherichia coli cells, which are not food-grade. It is explicitly stated if the cell wall of the host cell is not itself degraded by the lysin then the lysin secreting transformed host may be useful in suppressing populations of bacteria which are susceptible to lysis by the lysin. Nothing is mentioned regarding addition of a transformed host cell in improving cheese flavor, certainly not a transformed lactic acid bacterium.
As an alternative it is suggested in that patent specification "to encapsulate the lysin so that the timing of its addition is not important. The encapsulating agent dissolves after the cheese-making process is complete thus not affecting the starter bacteria before their role in acidification was complete."
This suggested alternative has the disadvantages, that (a) an encapsulating material has to be used, and (b) said material must not dissolve before the end of the cheese making process. Moreover, if the encapsulated lysin is added at the beginning of the cheese-making process, e.g. while adding the cheese starter culture to the milk, about 90% of it is removed with the whey. Thus one has to add about tenfold the required effective amount, which is economically not attractive. In a later publication C. A. Shearman, K. Jury & M. J. Gasson (Feb. 1992, ref. 2) described an autolytic Lactococcus lactis expressing a cloned lactococcal bacteriophaze .phi.vML3 lysin gene. In particular they stated that
"(e)xpression of the cloned lysin did not impair the ability of Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris strains to metabolize lactose, to clot milk and produce acid (data not shown)".
It was suggested that during the exponential phase the lysin would not, or would insufficiently be expressed. It would only be expressed in sufficient amounts to lyse an appreciable proportion of the cells during the stationary phase, which occurs at the end of the normal fermentation process. The article illustrates that maintenance of transformed lactococcal strains could be a problem. Maintenance at a temperature below 30.degree. C. slightly delayed the onset of lysis but at 30.degree. C. regrowth of lysin resistant bacteria occurred. As alternative buffering in a sucrose medium with a sucrose percentage higher than 20% was given. This does not seem to be suitable in a process of fermentation like cheese making where the fermentation step occurs at 30.degree. C. or higher and the presence of more than 20% sucrose is not acceptable.
Furthermore, at the end of that publication it was indicated that expression in the stationary phase is not completely controlled. In addition the use of osmotic buffer in a cheese maturing process is probably not very efficient timewise. This can be illustrated by the length of time required for a Gouda cheese immersed in a brine bath to achieve the desired degree of salt flavour. For this cheese type for example the osmotic effect of salt concentration is not going to be very quick. The cheddar cheese making process would probably be more suitable as the salt addition step is m
REFERENCES:
patent: 5326858 (1994-07-01), Lichenstein et al.
Buist Girbe
Kok Jan
Ledeboer Adrianus Marinus
Venema Gerard
Ketter James
Quest International B.V.
Sandals William
LandOfFree
Process for the lysis of a culture of lactic acid bacteria by me does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the lysis of a culture of lactic acid bacteria by me, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the lysis of a culture of lactic acid bacteria by me will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-78867