Optimized extraction of astaxanthin from shrimp shells treated by biological enzyme and its separation and purification using macroporous resin

The best enzymatic protease treatment of shrimp shells was identified by comparing the enzymatic hydrolysis effects of many different types of biological enzymes using fresh Arctic sweet shrimp as raw materials. The optimal enzymolysis conditions were determined using neutral protease as the best enzymatic protease. Among multiple macroporous adsorption resins, XDA-8 macroporous adsorption resin was preferable due to its static adsorption rate and desorption rate. The yield of astaxanthin (134.20 μg/g) after treatment with neutral protease was 3.7 times higher than that of the control group (36.03 μg/g). The yield of astaxanthin was obviously improved after enzymolysis of the shrimp shells. The purity of the astaxanthin was up to 87.34%, approximately 6508 times higher than that of the raw material. The production cost of astaxanthin would be greatly reduced by use of XDA-8 resin to obtain high-purity astaxanthin. This technique offers a high value-added utilization of shrimp shells.

Identification of a GDSL lipase from Streptomyces bacillaris and its application in the preparation of free astaxanthin

Astaxanthin shows multiple biological activities, but it is usually linked to different fatty acids and exists in the form of esters. The complexity of astaxanthin esters limits their application in the preparation of sophisticated drugs. Herein, a novel lipase from Streptomyces bacillaris that could hydrolyze astaxanthin esters, named OUC-Sb-lip12, was expressed in Bacillus subtilis. The active site of OUC-Sb-lip12 is probably composed of a dyad of Ser48 and His254, instead of a typical catalytic triad. The lipase was identified to be a GDSL hydrolase, and it showed highest activity at 45 °C and pH 9.0 (glycine-NaOH buffer). OUC-Sb-lip12 showed a good stability at its optimum temperature or a higher temperature, retaining 88.4% and 80.6% of its activity after incubating for 36 h at 45 °C and 55 °C, respectively. OUC-Sb-lip12 could effectively hydrolyze astaxanthin esters in Haematococcus pluvialis oil, generating free astaxanthin. Under the optimum conditions, 96.29% astaxanthin esters were hydrolyzed in 12 h. In addition, B.subtilis is a GRAS model strain and it could efficiently secrete lipase in 9 h, making the lipase potential for scale production of free astaxanthin, which could be further used in the preparation of specific astaxanthin esters with specific functions.