Analysis methods An aliquot of fermentation sample (20 ml) was filtered under vacuum through a 0.8 mm mixed cellulose esters membrane. The filtrate (extracellular broth) was appropriately diluted to determine the residual glucose concentration and the extracellular pigments concentration. The absorbance spectrum of the extracellular broth was recorded bya UV/VIS spectrophotometer (Unico, USA)from350nmto550nmat1nmintervals.Theabsorbanceunits(AU)atspecific wavelengths (410, 470 and 510 nm) were used as an index of the extracellular pigments concentration. The residual glucose was quantified by the standard 3, 5dinitrosalicylic acid (DNS) method.