Effects of algal–bacterial ratio on the growth and cadmium accumulation of Chlorella salina–Bacillus subtilis consortia

Abstract

Algae-bacteria consortia have been proven effective in the removal of metal pollutants, but the effects of algal-bacterial ratio in the metal accumulation and resistance by this symbiotic system have not been systematically investigated. In this study, we set up consortia with various ratios of Chlorella salina-Bacillus subtilis, determined their growth, Cd accumulation, levels of intracellular glutathione (GSH), extracellular polysaccharide, phosphorus (P) in the culture medium, and functional groups of consortia after Cd treatments (0.1, 0.5, 1 mg L −1 ) for 7 days. With the addition of B. subtilis in the C. salina culture, the dry weight and specific growth rate of the consortia significantly increased compared with C. salina alone, reaching 68.33 mg and 0.382 (mg L −1 ) d −1 respectively at the 1:4 algal-bacterial ratio with 1 mg L −1 Cd treatment. Maximum Cd removal (51.66%) was also observed upon the same Cd exposure and algal-bacterial ratio. Cadmium was mostly taken up into cells at 1 mg L −1 Cd whereas its adsorption dominated the accumulation when Cd was 0.1 and 0.5 mg L −1 . The amounts of extracellular polysaccharides, GSH, and P of the symbiotic system were also increased by the bacterial addition. Besides, Fouriertransform infrared (FTIR) spectroscopy analysis showed that functional groups like N-H, O-H, and P-O-C were involved in the Cd complexation. Taken together, a higher bacterial ratio promoted the Cd accumulation and detoxification by the C. salina-B. subtilis consortia through intra-and extracellular processes. K E Y W O R D S accumulation, algae-bacteria consortia, cadmium, detoxification 1 | INTRODUCTION Cadmium (Cd) is a toxic heavy metal and has been considered as a human carcinogen by the US Department of Health and Human Services [1]. It causes severe consequences in human health such as pathological changes in the liver, kidney, and other organs, neuralgia, osteoporosis, bone pain, and severe bone deformity [2,3]. Recently, Cd bioremediation has been extensively investigated due to its advantages such as cost-effectiveness

Copper Effect on Microalgae: Toxicity and Bioremediation Strategies

“…Although the development of a proper model to exploit the full potential of microalgae-bacteria consortium is still far to be established [126], the use of Microalga Growth-Promoting Bacteria (MGPB), as defined in different publications, seems to be a promising strategy to increase algal biomass and reduce heavy metals, or other pollutants, concentration [127]. In support, Yu et al, reported a more efficient Cd accumulation when a higher bacteria concentration was added to the mixed system composed by Chlorella salina and Bacillus subtilis [128]. An efficient treatment of Cu mine wastewater was obtained using immobilized sulphate-reducing bacteria beads with microalgae biomass as the sole nutrient sources [129].…”

Bioremediation of Metal-Polluted Industrial Wastewater with Algal-Bacterial Consortia: A Sustainable Strategy

“…Allam [40] carried out a comparative study on the bioremediation efficiency of HMs and dyes by individuals or consortia of bacteria (Bacillus subtilis, Rhizobium radiobacter and Sphingomonas paucimobilis) and found much higher removal efficiency results for Cd (96%). Yu et al [42] investigated the effects of algal-bacterial ratio on the Cd accumulation of Bacillus subtilis-Chlorella salina consortium and determined a lower value of Cd removal (51.66%) than the values in the present study.…”