The Relationship Between Enzyme Activities of Different Preparations and Their Ability to Stimulate Gas Production
If it were possible to identify precisely which enzyme activity was causing the fermentation response, it might be possible to develop better feed additive enzymes in a rational way. Indirectly, it would also have implications for our understanding of the microbial enzyme requirements in order to improve fiber digestion in the rumen. The enzyme activities of enzymes A and B and the cellulases were therefore compared with the
responses that had been observed in gas production.
Various glycosidase and polysaccharidase activities were measured in the enzyme extracts. β-Glucosidase activity was the highest glycosidase activity in all extracts,
whereas α-arabinosidase showed minor activity except in enzyme B (Table 5). Enzyme activity was compared with the impact of the different preparations on rates of gas production at the 11.1 mL/L concentrations presented in Tables 2 and 4 (Table 5). None of the glycosidase activities correlated highly with gas production from either corn silage or grass silage.
The highest correlation between polysaccharidase activity and gas production was found between the activity of enzyme extracts toward microcrystalline cellulose and their ability to stimulate gas production from corn or grass silage (Table 5). It should be noted in considering the correlations that the response in terms of gas production was not proportional to enzyme concentration(Tables 2 and 4), nor was the estimation of polysaccharidase activities. The measurement of glycosidase activities by the release of chromophores was straightforward, in the sense that the rate of reaction was related
linearly with enzyme concentration under the conditions of the assay. The measurement of polysaccharidase activities was not proportional to concentration, however, as illustrated in Figure 3. For example, the dye release from a 100-fold dilution was more than half that from a 10-fold dilution at 5 min, rather than onetenth of the activity as would be expected if enzyme concentration were limiting in classical Michaelis-Menten
kinetics. Also, although dye release was approximately linear with respect to time at the lowest concentrations of enzyme, the same was obviously not true at the highest concentrations (Figure 3). A similar lack of proportionality was found with CMCase and xylanase estimations by reducing sugar release (not shown). It was clear, therefore, that in order to assess properly the relationship between different enzyme activities
and their ability to stimulate fermentation, the response would have to be measured in incubation to which exactly equal amounts of activity had been
added.