Changing media can help, but do also try to express your protein at different temperatures. You don't write at which temperature you did your expression trials at, but do try 20 °C as well. Lower temperatures result in a slower expression, often improving the folding of the proteins.

hi. I tried expression at 18C 16hrs, 25C 8 hrs, 30C 6hrs, 12hrs, 37C 4 hrs with IPTG 0.1,0.2, 0.5, ).7 and 1mM with my GST tag clone in Rosetta pylsS cells.  I had tried expression in Bl21pylsS and rosetta pylsS.  Also with the his tag clone I had tried expressing it in the Artic express cells as well but expression was feeble. But in Rosetta I got a fantastic expression at 37C 1mM IPTG but all the protein was in the IBs. 

Co-expression with bacterial GroEL/GroES system may help to solubilise and improve yield of the recombinant protein of interest.

Protein expression can be improved by expression in strains co-expressing chaperone proteins such as these http://bit.ly/1SSmLUq . Yields will also improve if you codon harmonise the gene coding for your protein. You may also want to try expression under the control of a different induction system such as arabinose or tryptophan. Finally, for stubborn proteins which will not solubilise you should try a large cleavable solubility tag such as MBP.

Thanks everyone for your useful inputs. I am already on trying some of the ideas. 

Before trying such changes, it would be important to know which kind of Protein you are trying to express. Does it have a Signal Peptide? Maybe a Membrane anchor? These must be often removed. One or two amino acids can make a Major difference. You may send me the ID or sequence, and we can have a look to propose you an optibal Expression construct.