Process for the preparation of recombinant lectin protein

A method of preparing a recombinant lectin protein with improved cleavage of the initiator methionine, the method comprising expressing a recombinant lectin protein encoded by a recombinant lectin gene in a host cell in culture, wherein

• a. an induction phase is initiated by adding an inducer to the culture;
• b. the host cell is a recombinant E. coli cell, and expression during the induction phase is performed under conditions that cause the host cell to have a doubling time between 100 minutes and 160 minutes, wherein said conditions include the following:
• c. the induction phase is carried out at a temperature of at least 15° C. and no more than 22° C., and carbon to nitrogen ratio is maintained during the expression phase from 3:1 to 6:1;
• wherein the recombinant lectin protein is selected from
• i. SEQ ID NO:1;
• ii. SEQ ID NO:3;
• iii. SEQ ID NO:4;
• or
• iv. an amino acid sequence having at least 90%, 95%, 97%, 98%, or 99% homology with i, ii, or iii;
• d. the induction phase is carried out for at least 10 hours and the optical density of the culture is at least 25 and no more than 40;
• e. carbon source is added to the culture at a rate of from 0.5 to 2 gL-1h-1;
• f. the nitrogen source is added to the culture at a rate of from 0.4 to 1.5 gL” 1h-1;
• g. an inducer concentration of at least 0.1 mM and no more than 0.5 mM wherein the inducer is IPTG (isopropyl thio-galacto-pyranoside);
• h. purifying the crude recombinant lectin protein using at least one chromatography step,
• wherein by carrying out the induction phase under conditions e.g., resulting in a doubling time of 100 to 160 hours, cleavage of the initiator methionine is catalysed to reduce methionine residue in the recombinant lectin protein, and obtain a recombinant lectin protein in which less than 20% of recombinant lectin includes the initiator methionine.