Chemotaxis-associated biotechnology for the bacterial production of biofuel using blue carbon alginate

Brown algae are promising sources of blue carbon for biofuel production. The nonmotile Sphingomonas sp. strain A1 imports alginate, a major component of brown algae, by alginate-binding proteins AlgQ1/Q2 and an ATP-binding cassette transporter. Previously, we showed that metabolically engineered ethanol-fermentative strains A1 (A1-EPv14 and A1-EPv104) produced bioethanol from alginate and that repeated subculturing of strain A1 on soft agar plates inducibly activated motility, resulting in expression of chemotaxis toward alginate. This study examined the possibility of bioethanol production directly from brown algae, and what triggers chemotaxis and how chemotaxis affects ethanol yield. Strain A1-EPv104 produced ethanol from brown algae as well as alginate. Gene disruption and complementation revealed that AlgQ2, not AlgQ1, was involved in alginate chemotaxis. Compared with nonmotile strain A1-EPv14, strain A1-EPv14c exhibiting alginate chemotaxis produced ethanol from alginate more rapidly. This is the first report on chemotaxis-associated biotechnology for the rapid production of bioethanol from blue carbon alginate.