Yes it is partially growth associated. Factors which are required for the growth of the organism is key aspect.

That depends. In most cases yes it is growth related.

It normally is growth-associated. Enzyme is thermostable and some may think that it is also non-growth assocated. Practcally enzyme production is growth linked.

In my opinion you cannot say that amylase production (alpha- or gluco-) is "growth-associated" if by that you mean "constitutive" = always produced as a function of growth. If you grow e.g. Bacillus subtilis or Aspergillus awamori on glucose you will get loads of growth but zilch amylase. Amylase is in my opinion/experience an inducible secondary metabolite.

Depending on the growth conditions, yes, it is growth associated. But it has not a constitutive production!

Depending on the avaiable carbon sources, it will be expressed or not!

Liubov Sichel, Lytic Enzymes, LLC, Colorado, USA

My opinion is more close to Michael Bailey. Amylase is in my opinion/experience in large production is an inducible secondary metabolite and it production deeply depend not only from carbon quantity and type of sources but protein source and its predigestion - availability for the microbes. Carbon-protein combination will be critical for amylase production.

Practically enzyme production is growth linked but not always.

These enzymes are mostly associated with microbial growth. They are inducible in nature i.e. they are produced in response to presence of their respective substrate in microbiological media and help in producing metabolites primarily sugars which helps in growth of microorganisms, hence if you do some time course studies you will see that onset and increase of enyzme by microbes would be followed closely by microbial growth.

a) Looks like there are various different views here. But generally, how would you model amylase production in the presence of starch? To correlate it with the specific growth rate or no?

b) In the environment where initially only starch exists, I supposed the microbe would be "forced" to produce enzymes for cutting the starch chains thereby producing small sugars. But after that, in the presence of small sugars, does it mean that enzyme production will be reduced because small sugars which are easy carbon source are abundant thereby not requiring the microbes to secrete more enzymes for cutting starch chains?

c) Can microbes assimilate the starch, or it has to break starch down into small sugars before being assimilated for growth and maintenance?

Amylases are primary metabolites and hence the production is growth related.

I disagree with Sourav: amylases in e.g. Bacillus subtilis are catabolite repressed in the presence of e.g. glucose and however much growth you might and do get, there will be no production of amylase, except for some slight "production" after exhaustion of glc, during the starvation phase. Anyone can prove this to themselves, any time. If amylase were a primary metabolite, surely this would mean that it would always be produced? Or is this just a matter of definitions? Possibly...

In answer to Yong Kuen Ho: a) I'm no good at modeling! b) just so: small sugars cause catabolite repression and no continued production of (extracellular, inducible, secondary metabolite) amylase c) microbes cannot assimilate starch per se: they always have to hydrolyse it extracellularly with tightly catabolite-repressed amyalses so that they get enough sugar for themselves but do not produce so many free sugars that other microbes get a free lunch :-)

Expression of amylase genes is inducible by the presence of starch. Most pobably, the effect itself is exerted by small molecules (Maltose or isomaltose) resulting from breakdown of starch catalysed by low constitutive presence of amylase. The expression of amylase in firmicutes is subject to repression by glucose. Therefore, amylase production is not 'growth-related' or 'constitutive', but inducible. Nevertheless, one cannot say that amylase is a secondary enzyme because it plays a major role in catabolism when necessary. Promoters of various amylase genes have been shown to have similarity to sigma70 consensus of E. coli or to the veg promoter of B. subtilis which indicates that they are house-keeping genes. However, regulatory sequences (inverted or directed repeats) in the promoter upstream regions or overlapping with the -35 box are binding sites for repressors (such as MalR) which keep these promoters silent as long as gluose is present (or maltose absent)

I disagree with Surva and Hasna, while I agree with Dr. Baily and Ullrich. The enzyme is produced only in presence of starch. The production is altered after the starch has been converted to oligosacchrides. At this stage the microbe produes glucamylases to breakdown these oligosacchrides to glucose. Simply, you can do a ferementation experiment (for one week max.) and measure the amount of both reducing sugars and amylase activity in relation with time. You will find that at the end of fermentation period, the amylase activity decreases while the reducing sugars continue to increase althoough in abscence of the amylase activity.

Fermentation of cassava tubers was accompanied by a gradual decrease in pH, increased amylase activity in the steep liquor, and increased microbial load and lactic acid concentration. Amylase-producing bacterial strains associated with cassava fermentation were isolated and identified asBacillus subtilis, Bacillus licheniformis andBacillus cereus. The pH optima for the partially purified enzymes of these organisms were 7.0, 5.5 and 7.5, whilst their temperature optima were 30, 37 and 80°C. There was no significant difference in amylase activities when starch, dextrin, amylopectin, glucose and maltose were used as growth substrates.

In my opinion amylases are primary metabolites and therefore they are linked to growth. However, they are primary metabolites type II which means they are linked to growth but not at the maximum rate. This metabolites are suppressed by catabolite or another option is that they take a long time to be exported out of the cell. I suppose amylase is the same as lactase for example. Bacteria grows at their maximum rate in the presence of glucose but in this medium they do not produce lactase. You have to put a source of lactose, in this way they will produce the enzyme and they will grow but not at their maximum rate.