Ethanol production from ocean biomass
An object of the present invention is to provide a method for producing ethanol from polysaccharide alginate contained in a large amounts in brown algae, using the alginate assimilation capacity of the Sphingomonas sp. strain A1 and the strong ethanol production capacity of bacteria such as Zymomonas mobilis . Specifically, a method for producing ethanol using alginate as a raw material comprises causing genes encoding proteins and enzymes involved in Sphingomonas sp. strain A1-derived alginate assimilation and genes encoding enzymes involved in ethanol production to co-exist in a single microorganism and then culturing the microorganism in a medium containing alginate.
1. A method for producing ethanol using alginate as a raw material, comprising:
introducing a gene encoding pyruvate decarboxylase derived from Zymomonas mobilis and a gene encoding alcohol dehydrogenase derived from Zymomonas mobilis into a Sphingomonas sp. strain A1 which has an ABC transporter, alginate-binding proteins, endo-/exo-type alginate lyases, keto acid reductase, kinase, and aldolase, to obtain a transformed Sphingomonas sp. strain A1; and then
culturing the transformed Sphingomonas sp. strain A1 for 5 to 7 days by adding alginate or alginate oligosaccharide into a medium in an amount of 1 g/100 ml once per day starting from the third day of the culture, to produce a concentration of 0.7% (w/v) or more of ethanol in the medium,
wherein the gene encoding pyruvate decarboxylase derived from Zymomonas mobilis and the gene encoding alcohol dehydrogenase derived from Zymomonas mobilis are controlled by a Sphingomonas sp. strain A1-derived SPH2987 gene promoter consisting of the nucleotide sequence of SEQ ID NO: 25 and are thus expressed at high levels.
2. The method of claim 1 , wherein:
(i) the transformed Sphingomonas sp. strain A1 comprises multiple copies of the gene encoding pyruvate decarboxylase, multiple copies of the gene encoding alcohol dehydrogenase, or multiple copies of both genes;
(ii) the transformed Sphingomonas sp. strain A1 comprises a gene encoding formate dehydrogenase, which is an enzyme of an NADH regeneration system;
or both (i) and (ii).
3. The method of claim 1 , further comprising removing a gene involved in lactic acid synthesis from the transformed Sphingomonas sp. strain A1.
4. The method of claim 1 , wherein the transformed Sphingomonas sp. strain A1 is immobilized.
5. The method of claim 2 , wherein the transformed Sphingomonas sp. strain A2 comprises multiple copies of the gene encoding pyruvate decarboxylase, multiple copies of the gene encoding alcohol dehydrogenase, or multiple copies of both genes.
6. The method of claim 2 , wherein the transformed Sphingomonas sp. strain A1 comprises a gene encoding formate dehydrogenase, which is an enzyme of an NADH regeneration system.
7. The method of claim 2 , wherein
the transformed Sphingomonas sp. strain A1 comprises multiple copies of the gene encoding pyruvate decarboxylase, multiple copies of the gene encoding alcohol dehydrogenase, or multiple copies of both genes; and
the transformed Sphingomonas sp. strain A1 comprises a gene encoding formate dehydrogenase, which is an enzyme of an NADH regeneration system.
8. The method of claim 1 , wherein the culturing comprises adding alginate.
9. The method of claim 1 , wherein the culturing comprises adding alginate oligosaccharide.