1 23 Biotechnology Letters ISSN 0141-5492 Volume 40 Number 3 Biotechnol Lett (2018) 40:577-584 DOI 10.1007/s10529-017-2501-4 Functional characterization and substrate specificity analysis of Δ6-desaturase from marine microalga Isochrysis sp. S. Thiyagarajan, M. Arumugam, N. Senthil, S. Vellaikumar & S. Kathiresan