Method for producing methacrylic acid and/or ester thereof

A method, comprising contacting or culturing one or more microbes or genetically engineered strain thereof having an ability to produce methacrylic acid with a renewable raw material which gives rise to a biomass that acts as a carbon and/or energy source, wherein said methacrylic acid, an ester of methacrylic acid, or a mixture thereof can be produced from a pathway that utilizes isobutyric acid or valine,

• wherein the one or more microbes can grow on about 0.1 to 1% of valine as a sole nitrogen and/or carbon source, or about 0.1 to 1% of isobutyric acid as a sole carbon source and
• wherein the genetically engineered strain thereof is obtained by deletion or inactivation of one or more endogenous genes selected from the group consisting of enoyl CoA hydratase gene, 3-hydroxyisobutyryl CoA hydrolase gene, and 3-hydroxyisobutyric acid dehydrogenase gene.