What does respirometric analysis tell us about Metarhizium robertsii

Abstract

Metarhizium comprises species of importance as biological control agents whose conidia have been well produced in lab-scale packed column bioreactors. However, difficulties such as low oxygen supply, CO2 removal, and overheating limit bioreactor scale-up. To select suitable operating conditions in industrial-scale bioreactors, it is necessary to analyze the bioprocess in terms of O2 consumption and CO2 production. Metarhizium robertsii cultures reached maxima of O2 consumption and CO2 production rates of 0.23 and 0.35 mg/gidm h, respectively. The total O2 consumption (23.81 mg/gidm) and CO2 production (34.52 mg/gidm) were determined by experimental measurements and estimates by mathematical models with a coefficient of determination higher than 0.99. The respiratory quotient presented values from 1 to 1.2 (from 48 to 175 h). The respirometric analysis showed that the culture of is an aerobic process with low CO2 and low metabolic heat production, favoring the scale-up of the bioprocess