Growth promoting bacteria as value added in productivity of microalgae

Document Type : Original Article

Authors

1 Botany Department, Faculty of Science, Mansoura University, 35516 Mansoura City, Egypt

2 Botany Department, Faculty of Science, Mansoura University, 35516 Mansoura City, Egypt.

Abstract

Chlorella vulgaris was cultured on Bold’s Basal Medium (BBM). Three bacterial isolates coded as P3, P4 and P7 were isolated on Nutrient Broth medium (NB). Based on analysis of 16S rDNA of bacterial isolates, they were found to be contiguous similarity to Bacillus amyloliquefaciens, Pseudomonas rhizosphaerae, and Pseudomonas aeruginosa, respectively. C. vulgaris was cocultured with each bacterial strain at different concentrations, and it was found that the P4 bacterium had a growth-promoting effect on C. vulgaris, causing cell count to be increased six times greater than that of C. vulgaris axenic culture. Indole acetic acid (IAA) productivity was estimated for three strains of bacteria. It was found that the P4 strain has superiority in IAA productivity during culturing in  NB containing Tryptophan compared to  NB and recycled BBM (1.156±0.0097µǥ/ml, 1.064±0.0045µǥ/ml and 1.033±0.003 µǥ/ml), respectively. In contrast, P4 never produced IAA in fresh BBM medium. Furthermore, it was found that IAA produced by C. vulgaris upgraded to 0.987±0.0117 µǥ/ml. Moreover, it was found the highest cell number of C. vulgaris growing in coculture with P4 (1 algae:5 bacteria as v:v), although the highest culture density was investigated in the supernatant. Also, biomass productivity was highest in the supernatant than in P4 (1algae:5bacteria) 0.059±0.002 and 0.035±0.003 g/l/day, respectively. The highest ratio of chlorophyll a and chlorophyll b was in algae treated with P4 strain (1 algae:5 bacteria as v:v) recorded 2.447and 1.887 µg/ml respectively. Interestingly, the lipid productivity by C. vulgaris was the highest in the presence of IAA compared to axenic culture, being 1.608±0.124 f 1.176±0.164 g/l/day, respectively.

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