The present invention relates to a nucleic acid construct comprising: a nucleic acid sequence encoding an ice structuring protein (ISP) comprising the sequence set out in SEQ ID NO: 1 or a sequence at least 80% identical thereto or comprising the sequence set out in amino acids 21 to 261 of SEQ ID NO: 1 or a sequence at least 80% identical thereto； and, linked operably thereto, control sequences permitting expression of the nucleic acid sequence in a filamentous fungal host cell. The construct may be used in a method for the production of an ISP, wherein the ISP is expressed in a filamentous fungal host cell.
