ARS | Publication request: HETEROLOGOUS EXPRESSION OF FIBER-DEGRADING ENZYMES IN STREPTOCOCCUS BOVIS

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 7, 1996
Publication Date: N/A

Technical Abstract: Feed digestion in ruminant animals is primarily carried out by the dense, diverse population of microorganisms that inhabit the rumen. However, certain fractions of feed material such as xylan are not efficiently degraded. One approach that has been suggested to increase the digestion of xylan is to genetically modify bacteria that inhabit the rumen for increased production of xylan-degrading enzymes. Streptococcus bovis is a normal inhabitant of the rumen and can be a significant proportion of the ruminal population under certain dietary regimes. Ruminal strains of S. bovis are genetically distinct from strains isolated from humans and are capable of rapid growth on simple media. These traits and the ability to genetically manipulate S. bovis makes this organism a potential target for production of xylan-degrading enzymes. We now report on the expression of a Bacillus subtilis PAP.115 xylanase gene in S. bovis JB1. The gene encodes for a 22 kD protein and was introduced on the shuttle plasmid pVA838. The xylanase activity in crude extracts from S. bovis was 3-4 IU/mg protein, compared to 21 IU/mg for the purified enzyme from Escherichia coli. Further heterologous expression systems are being evaluated for secretion of this xylanase and other xylan-degrading enzymes. Expression of genes for xylan degradation may also make S. bovis a desirable candidate for use as a silage inoculant.