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These results show that the respiratory quotient is closely related to the physiological state of microorganisms and may be a determinable indicator for the efficiency of bioremediation. | Vietnam Journal of Science and Technology 55 (4C) (2017) 51-56 USING THE RESPIRATORY QUOTIENT AS A MICROBIAL INDICATOR TO MONITOR SOIL BIODEGRADATION Tran Thanh Chi*, Duy Trong Hieu School of Environmental Science and Technology (INEST), Hanoi University of Science and Technology (HUST), 1 Dai Co Viet, Hanoi, Vietnam * Email: chi.tranthanh@hust.edu.vn Received: 30 June 2017; Accepted for publication: 17 October 2017 ABSTRACT The effects of nutrient amendments on the variation in time of the respiratory quotient (RQ) were investigated in soil. Microbial activity measured by CO2 production, biomass growth determined by plate counts technique and residual contaminants quantified by gas chromatography analysis were monitored in order to check their relation to RQ fluctuations. RQ values in all treatments displayed significant fluctuations over time which were closely related to the phases of the respiratory response as well as to microbial growth. After pollutant addition, an increase of RQ occurred in all microcosms. RQ values decreased when high degradation activity and microbial growth took place. RQ values slightly increased in all microcosms at the end of the incubation. These results show that the respiratory quotient is closely related to the physiological state of microorganisms and may be a determinable indicator for the efficiency of bioremediation. Keywords: respiratory quotient, soil, biodegradation. 1. INTRODUCTION Bioremediation is a well-recognized method for the treatment of contaminated soil [1]. However, bioprocesses are often operated under sub-optimal conditions due to the difficulty of identifying on-line the limiting parameters to biodegradation. Respiratory quotient, which is the molar ratio of carbon dioxide production to oxygen consumption, can display variations depending on composition of the examined microbial community as well as their available growth substrates [2]. Therefore, respiratory quotient could provide a valuable tool for .
