(599bx) Effect of Nitrogen Source on Carotenoid Production By Rhodotorula Glutinis P4M422 in a Medium Based on Goat MILK Whey

Recently, interest in carotenoids from food industries is due to many health benefits that have been reported such as powerful antioxidant. This property could be attributed to their structure which presents an unsaturated chain. Carotenoids belong to the isopreonid group; being β–carotene and astaxanthin the most applied pigments in different areas such as food, beverages, sausages, cosmetics and aquiculture industries. Their high antioxidant ability has attracted mainly to researchers and the growing demand by industries for natural carotenoids have leaded to develop reliable and safes processes. Many reports in literature have described the production of microbial carotenoids highlighting the low cost production through the use of agroindustrial byproducts. Rhodotorula glutinis is widely distributed yeast in nature, and it is one of the most studied microorganisms to produce carotenoids. It is able to synthesize β–carotene using agro-industrial wastes that contain the nutrients necessary for the growth of microorganisms and reducing production costs. Mexico is among of the 20 countries worldwide with the highest production of goat milk [1] and Coahuila was the entity with the major production in 2009, reaching 58 thousand ton [2]. In Mexico, goat milk is mainly used by cheese industries, which leads to the availability of wastes from cheese production process, representing risks for environmental pollution. Goat milk whey from cheese-process is a waste rich in carbon source highly reliable to use in a fermentation process for the production of high value metabolites. The aim of this work was to analyze the effect of nitrogen source in a fermentation medium based on Goat Milk Whey (GMW) on production of carotenoids by Rhodotorula sp.  Rhodotorula glutinis strain from the collection of Food Research Department (FRD) was isolated in Nazas City, Durango, México from the Sotol process production. It was identified in the Molecular Biology Laboratory from FRD and preserved in YM agar slants. Goat milk whey was obtained from the center part of Coahuila from traditional cheese-producers. Cheese whey was de-proteinized by autoclaving (15 minutes at 120° C and 15 psi) and filtered, then also micro-filtered and finally hydrolyzed (β –galactosidase, Chr-Hansen, Germany) at pH of 6.5, temperature of 37 °C and 200 rpm of agitation. Three nitrogen sources were tested urea, sodium glutamate and yeast extract. Hydrolyzed Goat Milk Whey (HGMW) was supplemented with 3% of each nitrogen source. R. glutinis was propagated in YM medium (Glucose 1%, Yeast extract 0.3%, Malt extract 0.3% and Peptone 0.5%) during 24 h. Erlenmeyer flasks (125 mL) with 30 mL HGMW supplemented were inoculated with 1x10 ⁶ cells/mL and incubated by 72 h at 30 °C and 200 rpm. After fermentation samples, biomass was recovered by centrifugation (15 minutes at 4° C and 8,000 rpm) and washed twice with distilled water. Biomass was measured by constant weight in oven at 60° C overnight. Carotenoids were measured by spectrophotometry following the equation reported by Welburn [3] using DMSO. Results showed that all nitrogen sources used increased the carotenoids and biomass production. However, when urea was used as nitrogen source carotenoids concentration was higher in comparison with sodium glutamate and yeast extract (3018, 2012 and 2230 µg/L of total carotenoids). Biomass was increased noticeably by sodium glutamate and yeast extract in comparison with urea (10.6, 10.5 and 7.3 g/L of dry weight biomass). The three nitrogen sources analyzed increased the carotenoids and biomass yields regarding control samples (HGMW non-supplemented). In conclusion, urea was the most influential nitrogen source for carotenoids production representing a great alternative to develop a low-cost medium for carotenoids production by R. glutinis P4M422.

[1]  FAO. Goat milk production in Mexico: perspectives and situations, (2011).

[2]  SIAP. Goat milk production in Mexico: perspectives and situation, (2009).

[3] Welburn AR (1994) The spectral determination of chlorophyll a and chlorophyll b, as well as total carotenoids, using various solvents with spectrophotometers of different resolution. J Plant Physiol 144: 307-313.