Selective measurement of non-microbial protein in wastewater by use of Kjeldahl and adenosine 5'-triphosphate analysis

Abstract

We developed a procedure employing adenosine 5'-triphosphate (ATP) and total Kjeldahl nitrogen (TKN) measurements to estimate non-microbial protein concentration of dairy-processing wastewater; which also contains acid-producing microorganisms. Two different physiological conditions where maximum rates of acetic and butyric acid production occurred, which were pH 7.1 at 36.2 degrees C (Condition A) and pH 7.3 at 36.2 degrees C (Condition B), respectively, were tested in batch-mode in completely mixed bioreactors. The ratios of microbial nitrogen to ATP concentration were constant at post-lag phases, which were 23.2 mg N/mg ATP and 13.2 mg N/mg ATP for conditions A and B, respectively. Use of these conversion factors provides a simple and reliable way to measure the non-microbial protein concentration in acidogenesis of dairy-processing wastewater.