Fitzsimons, Aidan (1993) The development of novel silage inoculants using strain selection and genetic manipulation techniques. PhD thesis, Dublin City University.
Abstract
Eighteen strains of Pediococcus acidilactici were screened
in the laboratory for their potential as silage inoculants.
The grass silage isolate, P. acidilactici G24, was found to
be the most suitable, primarily on the basis of its short
lag phase. Inoculation of grass of water soluble
carbohydrate content greater than lOOg/kg DM with P.
acidilactici G24 at a rate of 106/g forage consistently
aided silage preservation, as indicated by a more rapid
rate of lactic acid production and pH decrease, and silage
with a lower pH, a lower ammonia nitrogen content and a
higher level of crude protein than uninoculated controls.
Furthermore, when compared to inoculants consisting of
Lactobacillus plantarum or mixtures of L. plantarum and P.
acidilactici, P. acidilactici G24 initiated a more rapid
rate of pH decrease and maintained the same silage pH up to
60 days after ensilage, implying that P. acidilactici G24
is superior to these more traditional inoculants.
When tested on grass of water soluble carbohydrate content
less than 60g/kg DM, P. acidilactici G24 failed to aid
preservation. A second inoculant was therefore developed to
cope with low water soluble carbohydrate conditions where
starch is available as an alternative source of water
soluble carbohydrate. This situation is frequently
encountered in the ensilage of alfalfa. While no amylolytic
strain of lactic acid bacteria suitable as a silage
inoculant could be isolated, the amylase enzyme of
Lactobacillus amylovorus was found to be well adapted to
typical ensiling conditions. A region of DNA coding for the
L. amylovorus a-amylase enzyme was therefore cloned and
integrated into the Cbh gene of the competitive inoculant
strain, L. plantarum LP80. A Lactobacillus host strain was
chosen in order to comply with regulations governing the
release of genetically engineered organisms into the
environment. The amylolytic derivative, L. plantarum
LPGAFA5, secreted 49% of the amylase secreted by L.
amylovorus, stably maintained amylase activity for 50
generations under non-selective conditions and displayed no
reduction in growth rates on glucose based media compared
to the parent strain, L. plantarum LP80.
Metadata
Item Type: | Thesis (PhD) |
---|---|
Date of Award: | 1993 |
Refereed: | No |
Supervisor(s): | O'Connell, Michael |
Uncontrolled Keywords: | Silage Fermentation; Grass research |
Subjects: | Biological Sciences > Biotechnology |
DCU Faculties and Centres: | DCU Faculties and Schools > Faculty of Science and Health > School of Biotechnology |
Use License: | This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License |
ID Code: | 18730 |
Deposited On: | 29 Jul 2013 10:16 by Celine Campbell . Last Modified 29 Jul 2013 10:16 |
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