Recombinant Expresion & Protein Production

(a) Proteins produced at higher temperatures denature the proteins by disrupting bonds that hold the molecules together. At lower temperatures, the bonds are less susceptible to molecular phase changes or more strongly held together. Think of ice water versus liquid water - the molecules in ice water are more strongly held together, but as soon as you apply heat, it increases disorder, causing the molecules to spread.

(b) Mammals have organelles that prompt proper protein folding, such as the endoplasmic reticulum. Bacteria don't have this luxury.

(c) Folding pathways in eukaryotes (yeast) are more structured/advanced/complex since they are modulated by numerous interactions with a variety of factors, including proteins such as chaperonins. This gives rise to more thermodynamically stable end-products.