When Anoxybacillus caldiproteolyticus 1A02591 was cultured with casein, 12 proteases were identified in the secretome, in which metalloproteases (6/12), and serine proteases (4/12) accounted for the majority and a thermolysin-like protease of the M4 family was the most abundant, suggesting that strain 1A02591 mainly secreted a thermophilic metalloprotease.