With the Nurbs2IGES toolbox found in MATLAB File Exchange https://www.mathworks.com/matlabcentral/fileexchange/12087-nurbs2iges
there are functions provided to export your surface to IGES. I don't think that you will need to change the order or the degree of the surface, and remember that a Bezier surface is a B-spline surface with knot vectors [0,...0,1,...,1] in the two parametric directions.