Bioengineering problems connected with the use of conventional and unconventional raw materials in fermentation. A review.

Some bioengineering problems connected with the use of conventional and unconventional raw materials in fermentation research and industry are reviewed. They include the effect of the physical state of different substrates (solid, liquid, gaseous) and considerations of physico-chemical processes, especially the identification of limiting steps. A new concept of classification of fermentors with respect to the macromixing properties is suggested and its applicability for different substrates is considered.