Co-culture of Penicillium sp. HSD07B and Candida tropicalis resulted in the production of a red pigment consisting of six components as determined by TLC and HPLC. The pigment showed no acute toxicity in mice and was mot mutagenic in the Ames test. The pigment was stable between pH 2 and 10 and temperatures of 10-100 degrees C and exhibited good photo-stability and resistance to oxidization by hydrogen peroxide and reduction by Na(2)SO(3). Glucose and ratio of C. tropicalis to strain HSD07B (w/w) in the inoculum were the important factors influencing production of the pigment. Under optimized conditions, a pigment yield of 2.75 and 7.7 g/l was obtained in a shake-flask and a 151 bioreactor, respectively. Thus, co-culture of strain HSD07B and C. tropicalis is a promising way to produce a red pigment potentially useful for coloring applications. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.