Effect of organic carbon to nitrogen ratio in wastewater on growth, nutrient uptake and lipid accumulation of a mixotrophic microalgae Chlorella sp.

This study investigated the biomass/lipid production, nutrient removal and fatty acid composition of an isolated mixotrophic microalga (Chlorella sp. G-9) cultured in simulated wastewater with different TOC/TN ratio. As the TOC/TN ratio of wastewater increased from 0 to 24, the growth rate of Chlorella sp. G-9 increased gradually, but did not increase further at 30. Nutrient removal was related to microalgae growth. In the wastewater with TOC/TN ratio of 24 and 30, 99.58% and 99.61% nitrogen was removed, respectively. In conditions of initial TOC/TN ratios of 24 and 30, Chlorella sp. G-9 could accumulate lipid as high as 35.3% and 36.5%, respectively. The corresponding lipid productivities were 34.2 and 32.6 mg L-1 d-1, respectively, which were 13.7 and 13.0 times higher than those in photoautotrophic condition. Increasing the initial TOC/TN ratio of the wastewater could slightly increase the saturated degree in fatty acid, thereby improving the stability of biodiesel.

Simultaneous nutrient removal and biomass/lipid production by Chlorella sp. in seafood processing wastewater.

Microalgae cultivation in wastewater has received increasing attention in recent years due to its many advantages. In this work, microalgae were cultured in seafood processing wastewater (SPW) for algal biomass and lipid production as well as nutrient removal. The biomass yield of Chlorella sp. achieved in the batch cultivation was 896 mg L-1, indicating that SPW contains a certain amount of nutrients which can be used for the growth of microalgae. However, the maximum specific growth rate of Chlorella sp. cultured in SPW throughout the whole cultivation period was only 0.040 d-1, suggesting that the growth of algal cells was inhibited during the culture process. High concentration of unionized ammonia in the SPW was found to be a factor inhibiting the growth of Chlorella sp. Aerated SPW (ASPW) and diluted SPW (DSPW) proved to be better culture media than SPW without pretreatment. The maximum specific growth rates of Chlorella sp. cultured in ASPW and DSPW during the culture interval were 0.156 and 0.091 d-1, respectively. Aeration pretreatment of SPW reduced the amount of toxic unionized ammonia, while most of the nutrients were retained in the wastewater. Therefore, higher biomass productivity (77.7 mg L-1 d-1) and higher lipid productivity (20.4 mg L-1 d-1) of microalgae were achieved in ASPW. Additionally, improved nutrient removal rates from ASPW were also achieved due to the faster growth of microalgae. The average nutrient removal rates in ASPW during the whole cultivation period were 4.98 and 1.91 mg L-1 d-1 for nitrogen and phosphorus, respectively.

The complete chloroplast genome of Gracilariopsis lemaneiformis, an important economic red alga of the family Gracilariaceae.

The complete chloroplast DNA (cpDNA) of a famous red alga of the family Gracilariaceae, Gracilariopsis lemaneiformis, was deduced by using next-generation sequencing and de novo assembly technology. The complete cpDNA of G. lemaneiformis consists of 182 505 bp and encodes 230 unique genes consisting 204 protein-coding genes (PCGs), 21 transfer RNA genes, 3 ribosomal RNA genes, 1 transfer-messenger RNA genes and 1 non-coding RNA genes. Among 204 PCGs, ccsA gene is interrupted by a intron. Unlike the typical quadripartite structure (a pair of inverted repeats separated by the small single-copy and large single-copy units) of cpDNA in higher plants, the complete cpDNA of G. lemaneiformis is very compact, containing no inverted repeat and just one copy of rRNA gene cluster consisting of 16S, 23S and 5S rRNA genes. The genic regions account for 83.7% of whole cpDNA genome, and the G + C content of the cpDNA was 27.4%. The low G + C content of G. lemaneiformis cpDNA is largely contributed by high A + T content in the PCGs and non-coding regions. A phylogenetic analysis of the 15 complete cpDNA from rhodophyta shows that G. lemaneiformis is closely related to macroalga Gracilaria salicornia. The complete cpDNA of G. lemaneiformis provides essential and important DNA molecular data for further phylogenetic and evolutionary analysis for rhodophyta.

The complete chloroplast genome of Wakame (Undaria pinnatifida), an important economic macroalga of the family Alariaceae.

We decoded the complete chloroplast DNA (cpDNA) sequence of the Wakame (Undaria pinnatifida), an important economic macroalga of the family Alariaceae, by using next-generation sequencing technology. The genome consists of 130 336 bp containing a pair of inverted repeats (IRs) of 4790 bp, which was separated by a large single-copy region and a small single-copy region of 77 821 and 42 934 bp, respectively. The genic regions account for 77.7% of whole cpDNA, and the GC content of the cpDNA was 30.6%. The U. pinnatifida cpDNA encodes 153 unigenes (129 protein-coding genes, 3 rRNA genes and 21 tRNA genes). There are 1 PCG (rpl33) and 1 tRNA genes (trnL) containing an intron. A phylogenetic analysis of the four complete cpDNA from Phaeophyceae showed that U. pinnatifida is closely related to Saccharina japonica with high bootstrap value supported. The complete cpDNA of U. pinnatifida provides essential and important DNA molecular data for further phylogenetic and evolutionary analysis for brown algae.

[Bioaugmented treatment of atrazine by genetically engineered microorganism in different bioreactors].

Removal of atrazine was investigated when genetically engineered microorganism (GEM) was inoculated into membrane bioreactor (MBR) and hybrid bioreactor for bioaugmentation. The performances of atrazine removal in two bioreactors were explored. The variations of GEM density and atzA gene abundance in two bioreactors were also determined. The results indicated that removal activities of COD and ammonia nitrogen were inhibited a little by atrazine and recovered after bioaugmentation by inoculated GEM. The better removal performance of COD and ammonia nitrogen was obtained in MBR. The biological removal efficiency of atrazine was improved significantly when bioaugmented treatment by GEM was applied. The atrazine removal increased gradually and the average removal rates reached up to 38.94% in MBR and 29.36% in hybrid bioreactor in the later running period. After inoculated, GEM densities in two bioreactors decreased rapidly and then tended to be constant. The stable GEM densities in MBR, suspended sludge and adherent biofilm of hybrid bioreactor were 5 x 10(3) CFU/mL, 1.1 x 10(3) CFU/mL and 0.4 x 10(3) CFU/mL, respectively. Fluorescence in situ hybridization (FISH) was used to detect azA gene in two bioreactors and the result indicated that the average relative abundances of atzA gene decreased initially and increased subsequently. The largest average relative abundance of atzA gene was obtained in MBR. The average relative abundance of atzA gene in adherent biofilm is larger than that in suspended sludge in the hybrid bioreactor. The horizontal transfer of atzA gene was the possible important reason responsible for high gene abundance.