EFFECT OF DIFFERENT SALINITY AND LIGHT INTENSITY ON THE GROWTH OF PORPHYRIDIUM CRUENTUM

In the study, Porphyridium cruentum was cultured under laboratory conditions at 20±2°C, 16:8 (light:dark) photoperiod and continuous aeration to different salinity (20‰, 30‰, 40‰) and two different light intensities (37 µmol m-2s-1 photon and 110 µmol m-2s-1 photon) and growth was determined. Dry matter, optical density and chlorophyll a parameter were used to determine growth. The best growth was determined in culture with a salinity of 30‰ at 110 µmol m-2s-1 photon light intensity. In this group, the optical density (OD) was 1.504±0.003 and the dry matter amount was 1.327gl-1. In the case of 37µmol µmol m-2s-1 photon light intensity, the optical density values were found to be similar in groups with 30‰ and 50‰ salinity and were found to be 1.234±0.004 and 1.215±0.002, respectively. The amounts of dry matter were also similar; 1.168gl-1 and 1.159gl-1, respectively. While the lowest growth was in the culture at 37 µmol m-2s-1 photon light intensity and 20‰ salinity. The optical density obtained on the last day of this group was 1.165±0.004 and the dry matter amount was determined as 0.986gl-1. The amount of chlorophyll a was determined in the cultured groups at the best 37 µmol m-2s-1 photon light intensity.

Transcriptomic survey reveals multiple adaptation mechanisms in response to nitrogen deprivation in marine Porphyridium cruentum

Single-cell red microalga Porphyridium cruentum is potentially considered to be the bioresource for biofuel and pharmaceutical production. Nitrogen is a kind of nutrient component for photosynthetic P. cruentum. Meanwhile, nitrogen stress could induce to accumulate some substances such as lipid and phycoerythrin and affect its growth and physiology. However, how marine microalga Porphyridium cruentum respond and adapt to nitrogen starvation remains elusive. Here, acclimation of the metabolic reprogramming to changes in the nutrient environment was studied by high-throughput mRNA sequencing in the unicellular red alga P. cruentum. Firstly, to reveal transcriptional regulation, de novo transcriptome was assembled and 8,244 unigenes were annotated based on different database. Secondly, under nitrogen deprivation, 2100 unigenes displayed differential expression (1134 upregulation and 966 downregulation, respectively) and some pathways including carbon/nitrogen metabolism, photosynthesis, and lipid metabolism would be reprogrammed in P. cruentum. The result demonstrated that nitrate assimilation (with related unigenes of 8–493 fold upregulation) would be strengthen and photosynthesis (with related unigenes of 6–35 fold downregulation) be impaired under nitrogen deprivation. Importantly, compared to other green algae, red microalga P. cruentum presented a different expression pattern of lipid metabolism in response to nitrogen stress. These observations will also provide novel insight for understanding adaption mechanisms and potential targets for metabolic engineering and synthetic biology in P. cruentum.

The effect of chitosan concentration on flocculation efficiency microalgae Porphyridium cruentum (Rhodhophyta)

Porphyridium cruentum is a species of red microalgae belongs to the family Porphyridiophyceae, divisi Rhodophyta. P. cruentum contains a lot of nutrients which are very useful as functional food. The purpose of this research is to determine the effect of chitosan concentration on the flocculation efficiency of P. cruentum. In this study, there were two treatments, namely the concentration of chitosan and the time of flocculation with 3 replications. Chitosan used were 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 ppm. The flocculation efficiency were carried out at 10, 20, 30 and 40 minutes. The highest density was reached on the seventh day as amount 1720x104cell/mL. The results showed that there was an effect of Chitosan concentration on flocculation efficiency (Anova two way; Fcount = 4.109; df (9; 80); p=0.01). In addition, there was an effect of flocculation time on flocculation efficiency (Anova two way, Fcount = 4.498; df (3;80)). Furthermore, there was an interaction effect between the chitosan concentration and the time of flocculation. (Anova two way; Fcount = 26.635; df (2;80)). The greater the value of chitosan concentration given the greater the value of flocculation efficiency.