Control strategies with variable air arrangements, forcefully aerated in single circular tray solid state bioreactors with modified Gompertz model and analysis of a distributed parameter gas balance

Figures & data

Figure 1. A perspective view of a single circular tray SSB from a side view, with emphasis on the location of the tray.

Figure 2. A schematic diagram of experimental set-up of the single circular tray SSB.

Table 1. Operating conditions of the solid state tray bioreactor.

Parameter	Value
Average wheat bran particle size	494.19 µm
Bulk density of wheat bran	0.37 g/mL
Particle density of wheat bran	1.19 g/mL
Porosity	67.29%
Initial moisture content	65%
Incubator room temperature	30 ± 3°C
Initial bed temperature	28 ± 3°C
Inlet air temperature	30 ± 2°C
Bed temperature sampling time interval	Every 60 min
O2/CO2 sampling time interval	Every 60 min
Fermentation period	72 h
Air flow rate	Various

Table 2. Air arrangement in single circular tray SSB.

Experiment	Air arrangement	Description
1	Control 1	No water, no air
2	Control 2	With water, but no air
3	Control 3	Dry air at flow rate 2 L/min is sparged from the bottom the bioreactor
4	Air flow rate = 1 L/min	Air moistened by passing through a reservoir of water at the bottom of the bioreactor
5	Air flow rate = 2 L/min
6	Air flow rate = 4 L/min
7	Air flow rate = 6 L/min

Figure 3. Profile of final moisture content at 72 h for control experiment (uninoculated wheat bran: □), fermented wheat bran with A. awamori (▪) and A. oryzae (

) growing in single circular tray SSB with different air flow rates. Dashed line represents initial moisture at 65%.

Figure 4. Variation of cumulative CO₂ evolved with time at different air flow rate during the growth of A. awamori [AA] and A. oryzae [AO] on wheat bran in single circular tray SSB. Symbols represent experimental data. The Gompertz model is shown as a solid line.

Table 3. Kinetics constants for different air flow rate according to Gompertz model.

Experiment (Flow rate – L/min)	A. awamori					A. oryzae
	CO2max (mole)	K (h^−1)	B	tmax (h)	R^2 coefficient	CO2max (mole)	K (h^−1)	B	tmax (h)	R^2 coefficient
Control 1	1.46	0.052	6.14	34.9	0.999	1.57	0.053	5.21	31.2	0.999
Control 2	1.35	0.043	5.22	38.4	0.999	1.38	0.054	6.44	34.5	0.997
Control 3	0.95	0.050	5.53	34.2	0.998	1.17	0.061	6.37	30.4	0.996
1	1.25	0.052	6.18	35.0	0.999	1.13	0.055	8.87	39.7	0.995
2	1.25	0.054	6.20	33.8	0.999	1.09	0.057	7.14	34.5	0.991
4	0.75	0.046	5.36	36.5	0.999	1.45	0.053	7.02	36.8	0.998
6	0.51	0.044	3.77	30.2	0.999	0.35	0.049	4.86	32.3	0.996

Figure 5. Correlation between measured and predicted data of A. awamori and A. oryzae from all experiments conducted using wheat bran in single circular tray SSB.

Figure 6. Profiles of RQ in single circular tray SSB systems with the fungi A. awamori [AA] and A. oryzae [AO] with different air arrangements. The straight line represents RQ =1.

Figure 7. Respiratory quotient (RQ) during SSF of A. awamori (▪) and A. oryzae (□) on wheat bran using single circular tray SSB with different air arrangements. The dashed line represents RQ =1.

Figure 8. Relationship between RQ with [${CO}_{2_{max}}$] obtained from every air arrangement using single circular tray systems with A. awamori and A. oryzae cultures.

Figure 9. Effect of the different air flow rate on the heat evolution of A. awamori [AA] and A. oryzae [AO] grown on wheat bran performed in single circular tray.