Rapid Measurement of Candida utilis Dry Weight with Microwave Drying

A microwave oven has been used to measure biomass concentration and construct a growth curve for Candida utilis ATCC 1084. Drying curve results show that when a sample was exposed to microwave radiation for 15 min, microwave and air oven dry weight results are within 4 mg of one another when dried at the "cook" power setting (approximately 630 W at full power). For biomass dry weight sample sizes of 147.74 and 14.42 mg, the sample weight was reduced to within 10% of the final air oven dry weight in less than 4 min. At the "defrost" power setting 7 min were required to reduce the sample weight to within 10% of the final air oven dry weight for the large sample. For the small sample, this point was not reached in 15 min. Microwave drying can be used to rapidly estimate microbial biomass concentration.