Abstract: The effects of different types of light (sunlight, darkness, red, yellow, blue and green) and nitrogen source (ammonium chloride, glycine, potassium nitrate, urea, lactalbumin hydrolysate and yeast extract) on the growth and pigment production of Serratia marcescens y2 were studied by solid-state culture and spectrometry. The results showed that darkness was favorable for microbial growth and pigment production. Green light resulted in the lowest biomass of Serratia marcescens y2 among all monochromatic lights tested along with large amounts of pigment leaks out of the cells and a high degree of leaking pigment. Conversely, red light caused the smallest change in the biomass of Serratia marcescens y2 and consequently, the least amount of pigment leaks and a low degree of leaking pigment were found. These findings demonstrate that the strain produces red pigment and therefore absorbs green light in the largest quantity, leading to the occurrence of photooxidative damage and consequent pigment leakage. All organic nitrogen sources tested had a growth-promoting effect on Serratia marcescens y2. All the organic nitrogen sources expect yeast resulted in an increase in pigment production by the strain and of them, glycine was the best source. Moreover, more pigments were produced by this strain in the presence of glycine compared to inorganic nitrogen sources. There results suggest that glycine can promote pigment production and the accumulation of pigments with different structures by altering their synthetic pathways.

Key words: bacterial pigment, culture condition, monochromatic light, glycine