## 3 Results and Discussion
### Optimization of Red Pigment Production by M. ruler OMNRC45  
Pigment productivity can be influenced by the microbial strain, medium composition, and fermentation conditions [36]. Hence, to maximize the yield of red pigments produced by _M. ruber_ OMNRC45, the environmental and culture conditions were improved. Carbon is an essential nutrient for the biosynthesis of cellular components, such as carbohydrates, proteins, and fats, and through oxidation, it provides the energy necessary for cells. For _Monascus_ spp., carbon plays a critical role in cell growth, metabolism, and pigment production [37; 38]. In the present study, different carbon sources (i.e., rice powder, wheat flour, corn flour, corn cob powder, and glucose) were used to improve the growth of _M. ruler_ OMNRC45 (in liquid medium) and its red pigment yield. The results presented in Figure 3a show that under the experimental conditions, rice powder was the best source of carbon for biomass and red pigment production. These results were consistent with the findings reported by [PERSON] et al. [29], who obtained the highest pigment yield using rice powder as a carbon source. Through the results obtained, the higher yield of red pigments in the case of using rice flour as a carbon source can be linked to its higher content of starch compared to other carbon sources used. This is supported by the results obtained by [PERSON] et al. [39], who indicated that the increase in the production of _Monascus_ pigments is directly related to the efficiency in \(\alpha\)-amylase production and starch degradation by _M. ruler_. Conversely, crushed corn cob did not lead to high growth or pigment yield, which could be attributed to the need for additional pre-treatment when using this substance to match the growth requirements of the fungal strain. For similar reasons, the source of nitrogen in the culture medium is an essential factor influencing microbial growth as well as the production of primary and/or secondary bioactive metabolites [40]. As secondary metabolites, the production of both intracellular and extracellular pigments is expected to be influenced (quantitatively and qualitatively) by the nitrogen source used. We investigated the effects of organic (peptone-urea) and inorganic (NH4 NO3-(NH4)2 SO4-KNO3) nitrogen sources on the growth  
Figure 3: Effect of carbon (**a**) and nitrogen (**b**) sources on biomass and total red pigment production by _Monascus ruber_ OMNRC45 in liquid medium. of _M. ruber_ OMNRC45 and extracellular red pigment productivity. As shown in Figure 3b, _M. ruber_ OMNRC45 cultured using peptone as the nitrogen source (in cultivation medium) showed the highest pigment yield. However, the increase in fungal biomass production using the same nitrogen source was not significant compared to the results obtained using ammonium sulfate and potassium nitrate. [PERSON] and [PERSON] [41] reported that the inclusion of peptone in the culture medium led to the highest red pigment yield by _Penicillium_ sp. and various other pigment-producing fungi. In this study, temperature and pH were considered important environmental and culture parameters for improving the yield of red dyes from _M. ruber_ OMNRC45. Cultivation temperature plays an important role in the rate of all microbial biochemical activities, including nutrient absorption, enzyme synthesis, and pigment production [42]. The optimum temperature for growth and production of dyes by _Monascus_ spp. has a wide range (from 25 to 37 \({}^{\circ}\)C) and primarily depends on the species [29]. Therefore, an experiment was conducted to determine the effect of different incubation temperatures (20-40 \({}^{\circ}\)C) on the biomass and red pigment yield from _M. ruber_ OMNRC45. The data obtained and presented in Figure 4a showed that 30 \({}^{\circ}\)C was the optimum temperature for maximum biomass and red pigment production.