Abstract: A nucleic acid constructs including a heterologous nucleotide sequence operably linked to a constitutively active promoter; a 5? recombination sequence at a 5? end of the construct and a 3? recombination sequence at a 3? end of the construct, wherein the recombination sequences are configured for homologous recombination into a genome of a microalgal host cell; and optionally a bacterial 5? untranslated region (5?UTR) between the 5? recombination sequence and the promoter, and a bacterial 3? untranslated region (3?UTR) between the 3? recombination sequence and the heterologous nucleotide sequence.