**Norihiko Misawa**

Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, Suematsu, Nonoichi-machi, Ishikawa 921-8836, Japan; E-Mail: nmisawa@ishikawa-pu.ac.jp; 

Tel.: +81-76-227-7525; Fax: +81-76-227-7557

*Received: 21 March 2011; in revised form: 19 April 2011 / Accepted: 26 April 2011 / Published: 6 May 2011* 

**Abstract:** Marine bacteria belonging to genera *Paracoccus* and *Brevundimonas* of the 

΅*-Proteobacteria* class can produce C40-type dicyclic carotenoids containing two Ά-end groups (Ά rings) that are modified with keto and hydroxyl groups. 

These bacteria produce astaxanthin, adonixanthin, and their derivatives, which are ketolated by carotenoid Ά-ring 4(4ȝ)-ketolase (4(4ȝ)-oxygenase; CrtW) and hydroxylated by carotenoid Ά-ring 3(3ȝ)-hydroxylase (CrtZ). In addition, the genus *Brevundimonas* possesses a gene for carotenoid Άring 2(2<sup>ȝ</sup>)-hydroxylase (CrtG). This review focuses on these carotenoid Άring-modifying enzymes that are promiscuous for carotenoid substrates, and pathway engineering for the production of xanthophylls (oxygencontaining carotenoids) in *Escherichia coli*, using these enzyme genes. Such pathway engineering researches are performed towards efficient production not only of commercially 

important xanthophylls such as astaxanthin, but also of xanthophylls minor in nature (e.g., Ά-ring(s)-2(2ȝ)-hydroxylated carotenoids). 

**Keywords:** *Paracoccus*; *Brevundimonas*; marine bacteria; ketocarotenoid; functional xanthophyll 
