*Article* **Optimization of Collagenase Production by** *Pseudoalteromonas* **sp. SJN2 and Application of Collagenases in the Preparation of Antioxidative Hydrolysates**

**Xinghao Yang 1,2,†, Xiao Xiao 1,†, Dan Liu 1, Ribang Wu 1, Cuiling Wu 1, Jiang Zhang 1, Jiafeng Huang 1, Binqiang Liao <sup>1</sup> and Hailun He 1,\***


Received: 18 October 2017; Accepted: 29 November 2017; Published: 4 December 2017

**Abstract:** Collagenases are the most important group of commercially-produced enzymes. However, even though biological resources are abundant in the sea, very few of these commercially popular enzymes are from marine sources, especially from marine bacteria. We optimized the production of marine collagenases by *Pseudoalteromonas* sp. SJN2 and investigated the antioxidant activities of the hydrolysates. Media components and culture conditions associated with marine collagenase production by *Pseudoalteromonas* sp. SJN2 were optimized by statistical methods, namely Plackett–Burman design and response surface methodology (RSM). Furthermore, the marine collagenases produced by *Pseudoalteromonas* sp. SJN2 were seen to efficiently hydrolyze marine collagens extracted from fish by-products, and remarkable antioxidant capacities of the enzymatic hydrolysates were shown by DPPH radical scavenging and oxygen radical absorbance capacity (ORAC) tests. The final optimized fermentation conditions were as follows: soybean powder, 34.23 g·L−1; culture time, 3.72 d; and temperature, 17.32 ◦C. Under the optimal fermentation conditions, the experimental collagenase yield obtained was 322.58 ± 9.61 U·mL−1, which was in agreement with the predicted yield of 306.68 U·mL−1. Collagen from Spanish mackerel bone, seabream scale and octopus flesh also showed higher DPPH radical scavenging rates and ORAC values after hydrolysis by the collagenase. This study may have implications for the development and use of marine collagenases. Moreover, seafood waste containing beneficial collagen could be used to produce antioxidant peptides by proteolysis.

**Keywords:** collagenase; fermentation optimization; collagen; *Pseudoalteromonas*; antioxidant peptides
