Turning leftover to treasure: An overview of astaxanthin from shrimp shell wastes

Often being labeled as king of carotenoids, the pigment astaxanthin is gaining more and more popularity in the recent years especially on its the recovery from crustacean wastes. Every year the crustacean processing industries produce tons of crustacean wastes, which when left unmanaged cease the recovery of astaxanthin and inevitably cause pollution to the environment. Residues from crustacean processing industries can be utilized as animal feed as the presence of astaxanthin gives good coloration and increases general health. As astaxanthin has many beneficial purposes, managing the wastes reduces certain industry's dependency on algae-produced astaxanthin. The history of crustacean waste processing in recovering astaxanthin began with chemical treatments. However, due to the chemical residue left behind, the trend has shifted to commercial enzymes. As purified commercial enzymes are expensive and are difficult to obtain, the process of pigment recovery further switches to a more ergonomically method by using microbial fermentations. Microbial fermentation is a mild degradation method and is less invasive in altering the properties of astaxanthin. Alternatively, astaxanthin can also be directly extracted from crustacean wastes using nonpolar solvents and/or a mixture of semipolar solvents. This review discusses on an overview of astaxanthin recovery from crustacean wastes, which include conventional and modern approach in obtaining astaxanthin, extraction methods, identification techniques, and the economy of astaxanthin. Additionally, the future prospects and challenges of the astaxanthin are also discussed.