TECHNOLOGY FOCUS - BIOLOGY - Preferred Method: The method further comprises culturing the host cell in the presence of at least a biological substrate for the polypeptide or a polypeptide encoded by the nucleotide sequence. The polynucleotide hybridizes to a complement of SEQ ID NO: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33 or 35 and/or its fragment, where the polynucleotide encodes a polypeptide having the same biological activity as a polypeptide comprising amino acid sequence of SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34 or 36. The polypeptide or the polynucleotide is derived from a cyanobacterium. The host cell produces a polypeptide encoded by the nucleotide sequence of the recombinant vector. The hydrocarbon is secreted by the host cell. Preferred Components: The polypeptide comprises amino acid sequence of SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, or 36 with one or more amino acid substitutions, additions, insertions, or deletions, where the polypeptide has decarbonylase activity. The polypeptide comprises amino acid sequence of SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34 or 36 with one or more conservative amino acid substitutions. The recombinant vector further comprises a promoter operably linked to the nucleotide sequence. The host cell is a mammalian cell, plant cell, insect cell, yeast cell, fungus cell, filamentous fungi cell or bacterial cell, preferably Escherichia coli cell, which is a strain B, C, K or W E. coli cell.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The substrate is a saturated fatty acid derivative, preferably 14-22C saturated fatty acid derivative comprising octadecenal, hexadecenal, methyl hexadecenal, methyl octadecenal (all preferred), 2-methyl icosanal, icosanal, tetradecanal, 2-methyl octadecanal, stearaldehyde, palmitaldehyde or their derivatives. In the biofuel, the hydrocarbon has a delta 13C of greater than or equal to -15.4, and an f(M)14C of at least 1.003. EXAMPLE - Genomic DNA encoding Synechococcus elongatus PCC7942 or f1593 (YP400610; putative decarbonylase) (SEQ ID NO: 1) (sequences not defined here may be found at ftp://ftp.wipo.int/pub/published_pct_sequences/publication) was amplified and cloned into NdeI and XhI sites of vector OP-183 (pACYC derivative) under the control of Ptrc promoter. The resulting construct was cotransformed with OP80-PCC7942-1594 into E. coli MG1655 and the cells were allowed to grown at 37 degrees C in M9 minimal media supplemented with spectinomycin (100 mu g/ml) and carbenicillin (100 mu g/ml). The cells were cultured and extracted with ethyl acetate (0.5 ml). The S. elongatus PCC7942-1593 in E. coli converted the hexadecanal and octadecenal into pentadecane and heptadecene, respectively.