Additional citation (no PMID) -- Kawahara K et al., (1994): Isolation of Sphingomonas Strains from Ears of Rice and Other Plants of Family Gramineae - Biosci. Biotech. Biochem. 58(3): 600-601.
A component of microorganisms, animal tissues and human tissues; together with oleic acid, a common octadecenoic acid of fruit pulp liquids. --Shibahara et al. (1987) (http://www.springerlink.com/content/m6889066v5248447/fulltext.pdf).