This work was concerned with the production of natural red pigments from submerged cultures of Monascus purpureus. The effect of three environmental factors on fungal growth and pigment production was elucidated, and techniques which enhance red pigment production were investigated.Recently, due to public interest in "natural" products, increasingly stringent regulation and health concerns with existing chemical colourants, the world colour industry has turned its attention to natural colourants, particularly in food and cosmetics applications. Modern biotechnology offers promise for producing red colourants from microorganisms, including Monascus pigments from the fungus Monascus purpureus, which provides orange and red colours with excellent properties as food colourants.-Previous works have explored the microbiology of Monascus fungi and the properties of Monascus pigments in detail. However, knowledge about the biosynthesis of these hexaketide Monascus pigments is very limited. A literature review revealed that pigment production is affected by culture method and environmental factors, including carbon and nitrogen source, phosphate and micronutrient concentrations, aeration/agitation, pH and temperature. Published results are confounded due to a low level of control over the culture environment and the crude method of analysis for the quantity and type of pigments.In this work, submerged shake flask and fermenter cultures of M. purpureus 192F were performed to study the effect of pH, nitrogen and carbon source on the production of Monascus pigments. In addition to the materials and methods described, a high performance liquid chromatograph (HPLC) method was used which identified the production of five out of six reported Monascus pigments, including monascorubramine (red), the orange pigments, rubropunctatin and monascorubrin, and the yellow pigments, monascin and ankaflavin, from the culture of M. purpureus 192F. The red pigment rubropunctamine was not detected.Shake flask cultures studies reproduced the results of previous work. Experimental results from pH-controlled batch fermenter cultures revealed that Monascus fungal growth and ankaflavin synthesis were favoured at low pH (pH 4), the latter probably accounting for the increase in yellow (A400nm) absorbance under these conditions. Production of the pigments monascm, rubropunctatin and monascorubramine was independent of pH.The nature of the nitrogen source affected fungal growth and pigment production, independent of pH. Ammonium and peptone supported better mycelial growth than nitrate. Monascorubramine was the major pigment product in all instances, while ankaflavin was not produced in nitrate cultures. Ammonium and peptone cultures produced four pigments, of which the production of monascin, rubropunctatin and ankaflavin were enhanced compared to those in nitrate cultures.Maltose promoted fungal growth and considerable pigment yield, particularly monascorubramine (maximum concentration 1.9 g/L), with ethanol produced at low concentrations. These results were reproduced by glucose at low (20 g/L) concentration, suggesting that the influence of carbon source was a glucose effect. A fed-batch culture with a continuous feed of glucose significantly improved the production of monascorubramine. The link among glucose concentration, ethanol production and biomass yield suggested that M. purpureus may be a respiration limited fungus, which under conditions of high glucose and oxygen concentrations, becomes respirofermentative. This hypothesis is proposed to account for poor biomass and pigment yields under these circumstances.A further hypothesis proposed is that ankaflavin is produced from monascin, this bioconversion being favoured at pH 4 and by the use of peptone.At pH 4, the absorbance of intracellular pigments, or the concentration of monascorubramine and monascin, reduced typically when glucose and the nitrogen source were depleted. Investigation of this pigment loss using a resting cell system suggested the presence of an enzyme degradation mechanism, which was sensitive to pH, the presence of catabolites and pigment type. Pigment degradation, particularly for orange (A470nm) and red (A500nm) pigments, was inhibited by the presence of glucose and peptone and at high pH (pH 7).This work provided information to enhance red pigment production in submerged cultures. Further development studies to apply these results industrially are discussed.