Identify the type of biological vector, naturally occurring in bacteria as a small circular loop of double-stranded DNA, that is used to carry the chymosin gene into the host cell.

Name the enzyme used to cut open this vector to create compatible 'sticky ends', and the enzyme used to permanently join the chymosin gene into the vector.

To optimize industrial-scale production of recombinant chymosin, these genetically modified bacteria are cultivated in a bioreactor.

Describe an investigation to determine how the incubation temperature of the nutrient broth affects the yield of recombinant chymosin produced by the bacteria.

Your answer should include experimental details and be written in full sentences and paragraphs.