Evaluation of the process conditions for the production of microbial carotenoids by the recently isolated Rhodotorula mucilaginosa URM 7409

Abstract

This study aimed to improve the physical and nutritional process conditions for the production of carotenoids by the newly isolated Rhodotorula mucilaginosa, a red basidiomycete yeast. The carotenoid bioproduction was improved using an experimental design technique, changing the process characteristics of agitation (130 rpm to 230 rpm) and temperature (25 °C to 35 °C) using seven experiments, followed by a 25-1 fractional design to determine the relevant factors that constitute the culture medium (glucose, malt extract, yeast extract, peptone and initial pH). A complete second order experimental design was then carried out to optimize the composition of the culture medium, the variables being yeast extract (0.5 to 3.5 g/L), peptone (1 to 5 g/L) and the initial pH (5.5 to 7.5), with 17 experiments. The maximum carotenoid production was 4164.45 μg/L (252.99 μg/g), obtained in 144 h in YM (yeast malt) medium with 30 g/L glucose, 10 g/L malt extract, 2 g/L yeast extract, 3 g/L peptone, an initial pH 6, 130 rpm and 25 °C, demonstrating the potential of this yeast as a source of bio-pigments. In this work, the nitrogen sources were the factors that most influenced the intracellular accumulation of carotenoids. The yeast R. mucilaginosa presented high production at a bench level and may be promising for commercial production.

Production of microbial carotenoids by Rhodotorula lactosa isolated in the Brazilian tropical savanna / Produção de carotenoides microbianos por Rhodotorula lactosa isolada na savana tropical brasileira

“…Yeast extract and peptone are described as excellent sources of nitrogen for obtaining different bioproducts. The use of low amounts of these sources can benefit the production of pigment, that is, a high C/N ratio [7,17,27,28]. In this study, the two nitrogen sources have significant but negative effects, indicating a decrease in these nitrogen sources and an increase in the carbon source.…”

“…Initial pH in the range of 5 to 6 made no difference but a starting pH of 4 did not result in good pigment production (except assay 9). The accumulation of carotenoids in pigmented microorganisms is highly dependent on the growing conditions, such as carbon source, nitrogen source, C/N ratio and initial pH [7,17,22,23]. Especially, glucose has a stimulating effect on the rate of cell growth.…”

“…During cultivation, portions of biomass were collected and centrifuged (3439 x g for 10 min). The content of total carotenoids was estimated by the spectrophotometric method described in previous studies [17,18].…”

Carotenoids and Some Other Pigments from Fungi and Yeasts

“…An increased rate of stirring led to an essential increase in carotenoid production by Rh. mucilaginosa [ 169 ]. The addition of 0.5 M NaCl to the fresh water used in the preparation of nutrient media for engineered carotenoids producing S. cerevisiae strain increased the production of β-carotene by almost two times.…”

“…The nitrogen sources were revealed as the main factors that most efficiently influenced the intracellular accumulation of carotenoids in yeast Rh . mucilaginosa [ 169 , 171 ]. Metal ions (such as Ba, Fe, Mg, Ca, Zn, and Co) and especially some trace elements (such as Al, Zn, and Mn) are very important for carotenoids synthesis in various species of Rhodotorula [ 170 ].…”