To meet the need for studies of anaerobic microbial and animal cell cultures involving much lower heat effects as compared to aerobic microbial cultures, a bench scale calorimeter, Bio-RCl, has been improved for achieving a higher long-term sensitivity. This newly improved Bio-RCl was used for heat measurement of anaerobic growth of Lactobacillus helveticus. The results showed that the bench-scale calorimetry has powerful potential for online monitoring and control of anaerobic bioprocesses as well as fundamental studies, such as stoichiometry, thermodn. and kinetics of cellular growth. [on SciFinder (R)]