Prior to joining the University of Hertfordshire, Allan was a research scientist with ICI, working on aspects of fungal physiology and plant tissue culture. His career as a Senior Lecturer at the University of Hertfordshire encompassed teaching in microbiology and research in microbial physiology and fermentation technology. Allan retired from the University and continued as a visiting lecturer but also combined his interests in microbiology and local history in his research into the history of brewing in Hertfordshire.Stephen's career as Senior Lecturer at The University of Hertfordshire has encompassed teaching in numerous fields across the Chemical, Biological and Environmental Sciences, together with research in effluent treatment, microbial physiology and fermentation technology. He was a member of the Society of Chemical Industry and a Fellow of the Higher Education Academy. Both Allan and Stephen have taken an advisory role in the development of this edition but the influence they had on the previous three editions very much remain as a foundation of the current book.