Practice question

Batch fermentation represents simplest closed system operation where all nutritional components, medium, precursors and inoculum are added at beginning, vessel sterilized, and no further input or output occurs except for aeration gases, acid-base addition for pH control and occasional sampling until harvest after complete cycle. Microbial population traverses classic growth curve including lag adaptation with enzyme induction, exponential phase where Monod kinetics mu equals mu-max times S over Ks plus S governs, stationary phase where nutrient exhaustion and organic acid accumulation limit growth, and death phase. Mass balance applies only to initial volume, simplifying sterility validation, instrumentation and batch record traceability per lot. Advantages include flexible product changeover, reduced contamination cross-over and suitability for secondary metabolites like penicillin that require full physiological differentiation. Downsides encompass downtime for cleaning and sterilization, lower volumetric productivity compared to continuous systems and initial substrate inhibition at high sugar concentrations above 100 g per L causing osmotic stress and overflow metabolism.