Abstract:Kinetic parameters describing growth and decay of mesophilic (30 degrees C) and thermophilic (55 degrees C) aerobic biomass were determined in continuous and batch experiments by using oxygen uptake rate measurements. Biomass was cultivated on a single soluble substrate (acetate) in a mineral medium. The intrinsic maximum growth rate ( micro (max)) at 55 degrees C was 0.71+/-0.09 h(-1), which is 1.5 times higher than the micro (max) at 30 degrees C (0.48+/-0.11 h(-1)). The biomass decay rates increased from 0.… Show more
“…Table 5 shows a two-fold increase in k d between mesophilic and thermophilic operation. This is within the range expected based on other related studies (Vogelaar et al, 2003;Abeynayaka, 2009).…”
Section: Specific Death Rate Constant K Dsupporting
A mathematical model was developed of an aerobic membrane bioreactor (MBR) treating effluent from a by-products facility at a sugar mill producing furfural, based on measurements of microbial kinetics and stoichiometry at different temperatures. The model was calibrated and validated against plant data using volumetric flow into the MBR and volumetric sludge wasting from the MBR as inputs. The model is able to predict steady-state and unsteady-state operation of the MBR under both mesophilic and thermophilic conditions, and the transitions between the two regimes. Comparison of model simulations and plant data suggests that thermophilic operation is advantageous, but it is less stable than mesophilic operation and frequent feed disruptions can have detrimental effects on MBR operation.
“…Table 5 shows a two-fold increase in k d between mesophilic and thermophilic operation. This is within the range expected based on other related studies (Vogelaar et al, 2003;Abeynayaka, 2009).…”
Section: Specific Death Rate Constant K Dsupporting
A mathematical model was developed of an aerobic membrane bioreactor (MBR) treating effluent from a by-products facility at a sugar mill producing furfural, based on measurements of microbial kinetics and stoichiometry at different temperatures. The model was calibrated and validated against plant data using volumetric flow into the MBR and volumetric sludge wasting from the MBR as inputs. The model is able to predict steady-state and unsteady-state operation of the MBR under both mesophilic and thermophilic conditions, and the transitions between the two regimes. Comparison of model simulations and plant data suggests that thermophilic operation is advantageous, but it is less stable than mesophilic operation and frequent feed disruptions can have detrimental effects on MBR operation.
“…This can be understood from the changes in components included in a with decreasing μ [19]. Figure 1Literature compilation of correlation between measured specific maintenance rates a and maximum relative growth rates μ max for various microbial species ( ж [1]; [10]; × [21];○ [22]; [23]; — [26]; [29]; [33]; [34]; [36]; [43]; [44]; [58]; [59]; + [60]).…”
Microbial maintenance is an important concept in microbiology. Its quantification, however, is a subject of continuous debate, which seems to be caused by (1) its definition, which includes nongrowth components other than maintenance; (2) the existence of partly overlapping concepts; (3) the evolution of variables as constants; and (4) the neglect of cell death in microbial dynamics. The two historically most important parameters describing maintenance, the specific maintenance rate and the maintenance coefficient, are based on partly different nongrowth components. There is thus no constant relation between these parameters and previous equations on this subject are wrong. In addition, the partial overlap between these parameters does not allow the use of a simple combination of these parameters. This also applies for combinations of a threshold concentration with one of the other estimates of maintenance. Maintenance estimates should ideally explicitly describe each nongrowth component. A conceptual model is introduced that describes their relative importance and reconciles the various concepts and definitions. The sensitivity of maintenance on underlying components was analyzed and indicated that overall maintenance depends nonlinearly on relative death rates, relative growth rates, growth yield, and endogenous metabolism. This quantitative sensitivity analysis explains the felt need to develop growth-dependent adaptations of existing maintenance parameters, and indicates the importance of distinguishing the various nongrowth components. Future experiments should verify the sensitivity of maintenance components under cellular and environmental conditions.
“…(0.38 h À1 at 64.58C; Matsché and Andrews, 1973) and for a mixed batch culture (0.2 h À1 at 558C; Vogelaar et al, 2003) compare favorably with the death rate values (0.125-0.39 h À1 ) obtained in the present study during the batch growth of G. thermoleovorans T80 at 608C. Compared to mesophilic conditions, between two-and tenfold increase in bacterial decay rate have been reported under thermophilic conditions (Konopka et al, 1999;LaPara and Alleman, 1999;Vogelaar et al, 2003).…”
Section: Discussionmentioning
confidence: 99%
“…Although higher microbial growth rates are expected at thermophilic temperature ranges (i.e., greater than 508C), specific growth rates are reported to be lower than those achieved at mesophilic temperature ranges as a result of much higher specific microorganism death rates and maintenance requirements at elevated temperatures (Kuhn et al, 1980;Matsché and Andrews, 1973;Vogelaar et al, 2003). In the current study we have examined the growth patterns and kinetics of the soil thermophile Geobacillus thermoleovorans strain T80 under a variety of growth conditions leading to rapid cell lysis.…”
Batch cultures of the thermophilic bacterium Geobacillus thermoleovorans T80 attained extremely high-specific glucose utilization rates leading to high specific growth rates, followed by extensive cell death and lysis with the onset of substrate exhaustion. The dramatic decrease in live cell numbers, as determined by flow cytometry, was accompanied by the release of soluble protein. Once the growth phase reached the point of commitment to lysis created by the impending exhaustion of substrate, the addition of extra carbon substrate did not halt the rapid death rate and lysis, although, towards the end of the exponential growth phase, the substrate was utilized producing only a small additional biomass concentration as a result of the net effect of cell growth and death. This lytic phenomenon was observed when a range of different carbon substrates (glucose, pyruvate, acetate, n-hexadecane, nutrient broth), as well as ammonium (the nitrogen source) in the presence of excess carbon source, reached near exhaustion. The rate and extent of cell death and the ensuing lysis depend on the culture growth rate. Cultures batch grown with a lower initial substrate concentration, or at a lower temperature, or at lower dilution rates for continuous-flow cultures, exhibited a lower rate and extent of cell death and lysis. Batch re-culture of the persister cells resulted in a behavior identical to that of the original culture indicating that these cells were not genetically modified. The glucose utilization, cell growth and death rates were mathematically described based on Monod kinetics and estimated values of pertinent biokinetic constants are reported.
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