Soft Sensor Modeling Method Based on SPA-GWO-SVR for Marine Protease Fermentation Process

Table 1

Correlation between auxiliary variables and key biological variables.

Auxiliary variables	Correlation degree
	Cell concentration	Matrix concentration	Enzyme activity
Temperature t	0.2457	0.2469	0.4236
Tank pressure p	0.7164	0.7051	0.5862
Dissolved oxygen concentration	0.8853	0.8452	0.9645
pH value	0.8729	0.9124	0.8166
Airflow l	0.5321	0.4712	0.7033
Motor speed r	0.1983	0.2210	0.1875
Tank volume	0.7088	0.6820	0.7040
Acceleration rate of acid flow μ	0.9441	0.9864	0.8769
Alkali flow rate η	0.9087	0.9753	0.8934
CO2 concentration CO2.con	0.8865	0.7922	0.7965
O2 concentration O2.con	0.7230	0.7894	0.7847