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Bisabolol is a functional ingredient in various health and cosmetic products and has antibacterial, antiinflammatory, and wound healing properties. (−)-α-Bisabolol is chemically synthesized and produced by steam distillation of essential oils extracted from Brazilian Candeia (Eremanthus erythropappus). To sustainably produce pure (−)-α-bisabolol, we previously engineered Escherichia coli to produce 9.1 g/L (−)-α-bisabolol via heterologous mevalonate pathways and (−)-αbisabolol synthase (BOS) from German chamomile, Matricaria recutita (MrBOS). BOS has only been reported in MrBOS and Brazilian Candeia (EeBOS). The limited availability of BOS has made it difficult to achieve high titer and yield and large-scale (−)-α-bisabolol production. We identified a novel BOS in globe artichoke (CcBOS) and examined its functionality in vitro and in vivo. CcBOS showed higher catalytic efficiency and (−)-α-bisabolol production rates than those from MrBOS or EeBOS. In fedbatch fermentation, CcBOS generated the highest reported (−)-α-bisabolol titer to date (23.4 g/L). These results may facilitate economically viable industrial (−)-α-bisabolol production.

Complete hydrolysis of κ-carrageenan produces two sugars, D-galactose and 3,6-anhydro-D-galactose (D-AnG). At present, however, we do not know how carrageenan-degrading microorganisms metabolize D-AnG. In this study, we investigated the metabolic pathway of D-AnG degradation by comparative genomic analysis of Cellulophaga lytica LIM-21, Pseudoalteromonas atlantica T6c, and Epulopiscium sp. N.t. morphotype B, which represent the classes Flavobacteria, Gammaproteobacteria, and Clostridia, respectively. In this bioinformatic analysis, we found candidate common genes that were believed to be involved in D-AnG metabolism. We then experimentally confirmed the enzymatic function of each gene product in the D-AnG cluster. In all three microorganisms, D-AnG metabolizing genes were clustered and organized in operon-like arrangements, which we named as the dan operon (3,6-d-anhydro-galactose). Combining bioinformatic analysis and experimental data, we showed that D-AnG is metabolized to pyruvate and D-glyceraldehyde-3-phosphate via four enzyme-catalyzed reactions in the following route: 3,6-anhydro-D-galactose → 3,6-anhydro-D-galactonate → 2-keto-3-deoxy-D-galactonate (D-KDGal) → 2-keto-3-deoxy-6-phospho-D-galactonate → pyruvate + D-glyceraldehyde-3-phosphate. The pathway of D-AnG degradation is composed of two parts: transformation of D-AnG to D-KDGal using two D-AnG specific enzymes and breakdown of D-KDGal to two glycolysis intermediates using two DeLey-Doudoroff pathway enzymes. To our knowledge, this is the first report on the metabolic pathway of D-AnG degradation.