pHgrowth

pHgrowth is a concept used in microbiology and bioprocess engineering to describe and quantify how the growth rate of an organism depends on environmental pH. It can refer to both the empirical relationship between growth rate and pH and to a compact descriptor derived from that relationship.

In practice, researchers measure growth rate across a range of pH values at fixed temperature and other controlled conditions. The resulting data are plotted as growth rate (mu) versus pH and can be modeled with functions such as Gaussian or other asymmetric curves. Key parameters often associated with pHgrowth include the pH optimum (the pH at which growth is maximal), the maximum growth rate, and a tolerance or width parameter that characterizes how sensitive growth is to deviations from the optimum. The pHgrowth curve may be described directly, or summarized by metrics such as the area under the curve or the full width at half maximum.

Applications of pHgrowth include optimizing fermentation processes, selecting strains with desired pH tolerance, and informing food safety and shelf-life assessments where pH fluctuates. It also supports comparative studies of acid or alkali tolerance among species or strains.

Limitations of pHgrowth arise from the interactions among pH, temperature, nutrients, osmolarity, and other environmental factors; growth rate is highly context dependent, and measurement noise can affect fits. Accurate modeling requires careful experimental design and consideration of covarying factors.

See also: pH, microbial growth, growth curve, optimum growth pH, bioprocess optimization.