Interactive Effects of Ceftriaxone and Chitosan Immobilization on the Production of Arachidonic Acid by and the Microbiome of the Chlorophyte Lobosphaera sp. IPPAS C-2047

Pharmaceuticals including antibiotics are among the hazardous micropollutants (HMP) of the environment. Incomplete degradation of the HMP leads to their persistence in water bodies causing a plethora of deleterious effects. Conventional wastewater treatment cannot remove HMP completely and a promising alternative comprises biotechnologies based on microalgae. The use of immobilized microalgae in environmental biotechnology is advantageous since immobilized cultures allow the recycling of the microalgal cells, support higher cell densities, and boost tolerance of microalgae to stresses including HMP. Here, we report on a comparative study of HMP (exemplified by the antibiotic ceftriaxone, CTA) removal by suspended and chitosan-immobilized cells of Lobosphaera sp. IPPAS C-2047 in flasks and in a column bioreactor. The removal of CTA added in the concentration of 20 mg/L was as high as 65% (in the flasks) or 85% (in the bioreactor). The adsorption on the carrier and abiotic oxidation were the main processes contributing 65-70% to the total CTA removal, while both suspended and immobilized cells took up 25-30% of CTA. Neither the immobilization nor CTA affected the accumulation of arachidonic acid (ARA) by Lobosphaera sp. during bioreactor tests but the subsequent nitrogen deprivation increased ARA accumulation 2.5 and 1.7 times in the suspended and chitosan-immobilized microalgae, respectively. The study of the Lobosphaera sp. microbiome revealed that the immobilization of chitosan rather than the CTA exposure was the main factor displacing the taxonomic composition of the microbiome. The possibility and limitations of the use of chitosan-immobilized Lobosphaera sp. IPPAS C-2047 for HMP removal coupled with the production of valuable long-chain polyunsaturated fatty acids is discussed.

The complete sequence of the chloroplast genome of the green microalga Lobosphaera (Parietochloris) incisa

We hereby report the complete chloroplast genome sequence of the green unicellular alga Lobosphaera (Parietochloris) incisa (strain SAG 2468). The genome consists of a circular chromosome of 156,028 bp, which is 72% A-T rich and does not contain a large rRNA-encoding inverted repeat. It is predicted to encode a total of 111 genes including 78 protein-coding, three rRNA, and 30 tRNA genes. The genome sequence also carries a self-splicing group I intron and a group II intron remnant. Overall, the gene and intron content of the L. incisa chloroplast genome is highly similar to that of other species of Trebouxiophyceae. In contrast, the L. incisa chloroplast genome harbors 88 copies of various intergenic dispersed DNA repeat sequences that are all unique to L. incisa.