Abstract
The cryptophyte Rhodomonas salina is widely used in aquaculture due to its high nutritional profile. This study aims to investigate the effect of salinity and pH on the growth, phycoerythrin concentrations, and concentrations of non-volatile umami taste active compounds of R. salina, using a design of experiment approach. Rhodomonas salina was cultivated in a flat-panel photobioreactor in turbidostat mode in a range of salinity (20–40 ‰) and pH (6.5–8.5). The strain was able to grow steadily under all conditions, but the optimal productivity of 1.17 g dry weight L−1 day−1 was observed in salinity 30 ‰ and pH 7.5. The phycoerythrin concentration was inversely related to productivity, presenting higher values in conditions that were not optimal for the growth of R. salina, 7% of dry weight at salinity 40 ‰, and pH 8.5. The identification of the umami taste of R. salina was based on the synergistic effect of umami compounds 5′-nucleotides (adenosine 5′-monophosphate, guanosine 5′-monophosphate, inosine 5′-monophosphate) and free amino acids (glutamic and aspartic acids), using the equivalent umami concentration (EUC). The results indicated that an increase in pH induces the accumulation of 5′-nucleotides, resulting in an EUC of 234 mg MSG g−1 at a salinity of 40 and pH 8.5. The EUC values that were observed in R. salina were higher compared to other aquatic animals, a fact that makes R. salina promising for further research and application in the food and feed sectors.
Highlights
Marine microalgae have a wide range of commercial and industrial applications (Spolaore et al 2006; Chu 2013; Khatoon and Pal 2015)
This study aims to investigate the effect of salinity and pH on R. salina growth, phycoerythrin, and Free amino acids (FAAs) concentrations in a D-optimal design
The centre point of the D-optimal design was reproducible with a biomass concentration of 1.3 ± 0.04 g L −1, a growth rate of 0.82 ± 0.04 day−1, a biomass productivity of 1.07 ± 0.07 g
Summary
Marine microalgae have a wide range of commercial and industrial applications (Spolaore et al 2006; Chu 2013; Khatoon and Pal 2015). They have been introduced to the human diet for thousands of years and have been utilised as high-value food (Borowitzka 1998; Varfolomeev and Wasserman 2011; Hudek et al 2014). Free amino acids (FAAs) are associated with the characteristic taste of marine food. FAAs contribute to different degrees to the five primary tastes of food (sweetness, sourness, saltiness, bitterness, and umami) according to their side chains (Shallenberger 1993; Kawai et al 2002). The biochemical composition and sensory characteristics of oysters are attributed to the dietary composition, indicating that the flavour characteristics of algae can be carried through to the fed organism (van Houcke et al 2017)
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