Application of Food-Grade Proteolytic Enzyme for the Hydrolysis of Regenerated Silk Fibroin from Bombyx mori

Table 1

The specific enzyme activities of food-grade enzymes and the results of enzymatic hydrolysis of regenerated silk fibroin during 3 h reaction.

Food-grade enzyme	Specific activity (U/mg)	Conditions		Enzymatic hydrolysis
		pH	Temperature (°C)	Residual protein (%)	Amino acid (mg/L)
Alcalase® AF 2.4 L	14.0 ± 0.66	8.0	60	71.8 ± 1.07^b	2,209 ± 37.7^ab
Alphalase® NP	4.86 ± 0.18	7.0	60	84.4 ± 0.53^d	2,074 ± 25.8^c
Bromelain BR1200	0.10 ± 0.00	7.0	50	98.2 ± 2.39^h	580 ± 87.4^f
Collupulin™ MG	2.09 ± 0.02	6.0	60	92.4 ± 0.71^f	1,228 ± 40.8^e
Flavourzyme® 500 MG	2.38 ± 0.02	7.0	50	^(1)54.0 ± 1.67^a	2,011 ± 90.7^c
FoodPro® alkaline protease	15.0 ± 0.80	8.0	60	78.0 ± 0.19^c	2,271 ± 51.8^a
Neutrase™ 0.8 L	1.72 ± 0.02	7.0	50	97.1 ± 0.16^g	489 ± 69.6^f
Promod™ 192P	^(2)0.59 ± 0.01	5.0	50	NA	NA
Promod™ 278MDP	0.88 ± 0.01	7.0	60	90.8 ± 0.40^f	1,461 ± 12.4^d
Promod™ 279MDP	^(2)2.62 ± 0.05	5.0	60	NA	NA
Protamex®	3.11 ± 0.03	7.0	50	81.8 ± 2.51^e	2,118 ± 89.6^bc

⁽¹⁾The silk fibroin started to precipitate during the enzymatic reaction with Flavourzyme. ⁽²⁾Enzymatic reaction was performed at pH 7 instead of pH 5 as the substrate precipitated at acidic pH 5. NA: enzymatic reaction was not observed as these enzymes are classified as exotype proteases. a–g: means in the same column followed by different letters differ significantly ().