I knew it was a mistake to check in on this....
You don't need a bag of nutrients the size of a Sathanas, you establish a mining operation using the miners we already know the Shivans have, you then place the seed in a suitable location and begin to supply it with nutrients, the ship would then begin to construct it's own under-structure using the materials supplied, if there are no materials for the cells to use, then they simply won't do anything, a ship is not going to starve to death because it is not 'alive' in the standard use of the word. The power could be supplied using non biological means, which means a vast supply of readily convertible energy is on-hand for the genetic construction mechanisms.
The various materials would be fed into a chamber where enzymes would form them up into various required materials, unused material would be either ejected, or, more likely, recycled and stored. once processed, they could be fed to a capillary system that runs throughout the ship, much like the veins in a leaf, where the material would be secreted to a precise 'blueprint' defined by the genetic code, that can be done via either 'formers' which force the secretion to grow into a particular shape, or 'limiters' which re-absorb any material that does not correspond to the blueprint, both cell types have analogies in naturally occurring biology.
Once construction is complete, the secretion hardens, the veins close and most of the building 'engine' suffers from triggered cell death, or is stored in a 'holding area' much like the Spleen, ready to be released and duplicate itself when required to, for repair operations etc.
Animals grow in a womb, but the only womb a plant needs is the seed, with correct biological programming, a constant supply of nutrients, and a power source that is far higher than that supplied by normal sugar-absorbtion techniques such as digestion and photosynthesis, coupled with the fact that the whole structure is capable of making it's own 'builder cells', so 1 cell makes 2, 2 cells make 4 etc, I'd guesstimate a Sathanas-type biomass could be created in under 2 years.
I once remember a lesson my lecturer taught about starlings, every female starling has an average of 4 chicks per year, of those 4 chicks, they are lucky if 1 survives. However, if every single chick survived for every single starling, within 30 years, Earth would be solid Starling to a depth of 3/4 mile. If you consider the starlings as the 'cells' of the Biomass, it gives a good feel to how quickly things can move, only the Biotech could replicate far faster and, with the right mechanisms, without mutation.