Cunninghamella bainieri 2A1 is an oleaginous fungus whose lipid accumulation profile is significantly influenced by metal ion concentrations in growth medium. Mg2+, Fe3+, Mn2+ and Cu2+ were found to be the important elements affecting lipid accumulation in this fungus. This study employs a statistical method (Response Surface Methodology -RSM) to study the combined effects of Mg2+, Fe3+, Mn2+ and Cu2+ on lipid accumulation of C. baineri 2A1. Cultivation was carried out in 250 mL Erlenmeyer flasks containing 100 mL nitrogen limited medium at 30 degrees C and 250 rpm agitation for 120 h. A thirty-run central composite design experiment was employed to identify and optimize the significant factors. In addition to Mg2(+) and Fe3(+) which were shown to have significant effects on lipid accumulation, the interactions between Mg2+ and Cu2+, as well as the effect of Cu2+ in quadratic terms were also found to have significant effect on the process (p< 0.05). The highest amount of lipid obtained in this study was 39% g/g biomass with optimal levels of Mg2+, Fe3+ and Cu2+ at 5.00, 0.017 and 0.0005 g/L, respectively, while Mn2+ was omitted. A 32% increment in lipid yield was recorded, where the lipid content increased to 38%, compared to initial yield of 29% g/g biomass prior to optimization. In conclusion, Mg2+ and Fe3+ have significant positive effect on the lipid accumulation of this fungus, whereas Mn2+ and Cu2+ exert negative effects in combination.

Inoculum for a local isolate of oleaginus fungi, Cunninghamella bainieri 2A1 was developed by establishing the inoculum types, age and size for growth, lipid and gamma linolenic acid (GLA) production. Cultivation was carried out in 500 mL shake flask containing 200 mL of nitrogen limiting medium at 30 degrees C and 250 rpm agitation. Direct inoculation of spores into the production cultures gave higher productivity of lipid production 0.71 (g/L/day) than using 24 and 48 vegetative cells cultures which gave only 0.51 and 0.45 (g/L/day), respectively. Besides, production of GLA (5.3 x 10(-2) g/g lipid less biomass) in the cultures which directly inoculated with spores (1 x 10(5) spores/mL) was 23% higher than those produced in the cultures started with vegetative cells. Spore concentration of 1 x 10(3) spores/mL produced pelletal growth in size of 1.04 mm which contain 40% (g/g biomass) lipid and 8.34 x 10(-2) (g/g lipid less biomass).

The effects of ammonium tartrate and glucose concentration on biomass, lipid and GLA accumulation in Cunninghamella sp. 2A1 were investigated using Response Surface Methodology (RSM). Cultivation was carried out in 250 mL shake flask containing 100 mL of nitrogen limiting medium (with various combinations of concentration of ammonium tartrate (1-3 g/L) and glucose (30-60 g/L) at 30 degrees C and 250 rpm agitation for 120 h. The concentration of both compounds significantly affected the biomass, lipid and GLA yield (p<0.05), with the production of each of them being represented by quadratic models. Higher concentration of ammonium tartrate and glucose (2.99 and 59.33 g/L, respectively) was required for enhanced biomass production whereas low nitrogen content with excess glucose was otherwise favoured for lipid and GLA production. Ammonium tartrate and glucose concentration at 1 and 43 g/L, respectively were estimated by the model and proven to give the highest lipid production and GLA yield of 31.06 % (g/g biomass) and 4.15 x 10(-2) (g/g lipid less biomass), respectively.