Solid State Fermentation

Cheese is a solid state fermentation and, in smear cheeses, the surface microflora a biofilm. Both these modes of growth have been the subject of increasing interest and renewed research. Looking at cheese from these perspectives may offer new tools and new insights. The cheese matrix is a solid state fermentation but it differs from many of the new solid state fermentations which are being developed, often aerobic fungal processes, but it shares many of the same challenges in the measurement of system parameters and spatial heterogeneity. The importance of water availability (aw) and temperature as controlling factors on both the organisms capable of growth and their performance are implicit in the cheese-making process but perhaps not as explicitly controlled and manipulated as in solid state fermentation processes. The study of biofilms is important in pathogenesis, fouling and environmental microbiology and, unlike in the laboratory and many industrial processes, most microorganisms grow in biofilms rather than as planktonic growth in suspended liquid culture. Liquid culture lends itself to sampling and the measurement of the average properties of a population whereas cells in biofilms are spatially heterogeneous and form phenotypically differentiated subpopulations in which it is challenging to measure the properties of individual cells dynamic across spatial and temporal timescales. New technological approaches in this area are making these studies tractable and throwing up surprising complexity and sophistication relevant to understanding the behaviour of microorganism in and on cheese.