http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Breaking dormancy: an energy-efficient means of recovering astaxanthin from microalgae
Praveenkumar, Ramasamy,Lee, Kyubock,Lee, Jiye,Oh, You-Kwan The Royal Society of Chemistry 2015 GREEN CHEMISTRY Vol.17 No.2
<P><I>Haematococcus pluvialis</I>, in the dormant aplanospore (cyst) status after 30 d of cultivation, accumulates high levels of a superpotent antioxidant, astaxanthin, which has been demonstrated to have enormous therapeutic benefits. However, owing to the robust structure of its trilayered cell wall, the recovery of astaxanthin from the cyst cells remains an energy-intensive process. In the present study, a novel strategy utilizing a short-period germination based on the natural life cycle of <I>H. pluvialis</I> was developed as an energy-efficient pretreatment for the extraction of astaxanthin using ionic liquids (ILs) as green solvents. The germination resulted in damage and deconstruction of the cyst cell wall, and thereby facilitated the extraction of astaxanthin by ILs at room temperature. By this natural pretreatment with 1-ethyl-3-methylimidazolium ethylsulfate for a very short reaction time of 1 min, a high astaxanthin yield of 19.5 pg per cell was obtained, which was about 82% of a conventional volatile organic solvent extraction by strong, 30 000 psi French-pressure-cell homogenization. The maximal astaxanthin-extraction yield from <I>H. pluvialis</I> cells was observed for 12–18 h germination. The germination rate furthermore could be improved by manipulating the nutritional composition (especially the nitrate concentration) of the culture medium. In light of these results, it can be posited that natural germination following the principles of green chemistry can be a uniquely simple method of robust microalgal cyst cell pretreatment and extraction of astaxanthin with room-temperature ILs.</P> <P>Graphic Abstract</P><P>A highly energy-efficient natural pretreatment process of germination to assist ionic liquid-based extraction of astaxanthin from <I>Haematococcus pluvialis</I> is developed. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4gc01413h'> </P>
Praveenkumar, Ramasamy,Gwak, Raekeun,Kang, Mijeong,Shim, Tae Soup,Cho, Soojeong,Lee, Jiye,Oh, You-Kwan,Lee, Kyubock,Kim, Bongsoo American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.40
<P>Milking of microalgae, the process of reusing the biomass for continuous production of target compounds, can strikingly overcome the time and cost constraints associated with biorefinery. This process can significantly improve production efficiency of highly valuable chemicals, for example, astaxanthin (AXT) from <I>Haematococcus pluvialis</I>. Detailed understanding of the biological process of cell survival and AXT reaccumulation after extraction would be of great help for successful milking. Here we report extraction of AXT from a single cell of <I>H. pluvialis</I> through incision of the cell wall by a gold nanoscalpel (Au-NS), which allows single-cell analysis of wound healing and reaccumulation of AXT. Interestingly, upon the Au-NS incision, the cell could reaccumulate AXT at a rate two times faster than the control cells. Efficient extraction as well as minimal cellular damage, keeping cells alive, could be achieved with the optimized shape and dimensions of Au-NS: a well-defined sharp tip, thickness under 300 nm, and 1–3 μm of width. The demonstration of regenerative extraction of AXT at a single cell level hints toward the potential of a milking process for continuous recovery of target compounds from microalgae while keeping the cells alive.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-40/acsami.5b07651/production/images/medium/am-2015-07651u_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b07651'>ACS Electronic Supporting Info</A></P>
윤미라,오유관,Ramasami Praveenkumar,서영수,조순자 한국생물공학회 2017 Biotechnology and Bioprocess Engineering Vol.22 No.2
To investigate the effects of bacteria contaminated in microalgal cultivation, several bacteria were isolated from four photobioreactors for Chlorella sp. KR-1 culture. A total of twenty-one bacterial strains isolated from the reactors and identified by 16S rRNA gene sequencing. Six bacteria, which were found from more than two reactors of the four photobioreactors, were introduced into co-culturing experiments with Chlorella sp. KR-1. Then, the bacterial influences on the productivity of microalgal biomass and lipids were assessed in the photoautotrophic- and mixotrophic microalgal cultivation by comparing them with axenic culture of Chlorella sp. KR-1. The results showed that both biomass and lipid production were significantly enhanced under mixotrophic conditions compared to photoautotropic conditions. However, an excess ratio (more than 10%) of bacterial cells to microalgal cells at the initial stage of mixotrophic cultivation has limited the growth of Chlorella sp. KR-1 because of the relatively fast growth of bacteria, especially under mixotrophic conditions. Moreover, it was proven that the strong biofilm formability of Sphingomonas sp. MB6 is the responsible strain to cause the biomass aggregation observed during the early stage of co-culture. The high abundance of Sphingomonas sp. MB6 during early cultivation period shown by qPCR results was also well corresponded with the period shown a strong biofilm formation, which suggested the applicability of qPCR to monitor a specific bacterial group in a microalgal culture.
Seo, Jung Yoon,Praveenkumar, Ramasamy,Kim, Bohwa,Seo, Jeong-Cheol,Park, Ji-Yeon,Na, Jeong-Geol,Jeon, Sang Goo,Park, Seung Bin,Lee, Kyubock,Oh, You-Kwan The Royal Society of Chemistry 2016 GREEN CHEMISTRY Vol.18 No.14
<P>Microalgal biofuel, albeit an exciting potential fossil-fuel-replacement candidate, still requires the development of more advanced downstream processing technology for its price competitiveness. The major challenge in a microalgae-based biorefinery is the efficient separation of microalgae from low-concentration culture broth. The post-harvesting cell-disruption step necessary to render microalgae suitable for lipid extraction, moreover, further raises energy consumption and cost. For the mitigation of biorefinery complexity and costs, we suggest herein a new scheme that integrates the critical downstream processes (harvesting and cell disruption) by means of cationic surfactant-decorated Fe3O4 nanoparticles. The cationic surfactants' quaternary ammonium heads play an important role in not only flocculating negatively charged microalgae but also weakening thick cell walls. In the present study, the harvesting efficiency and cell-damaging effects of three cationic surfactants - cetrimonium bromide (CTAB), cetylpyridinium chloride (CPC), and cetylpyridinium bromide (CPB) - were evaluated. The CTAB-decorated Fe3O4 nanoparticles, which were found to be the most effective, achieved a 96.6% microalgae harvesting efficiency at a dosage of 0.46 g particle per g cell. Next, for the purposes of magnetic nanoparticle recycling and high-purity microalgal biomass obtainment, microalgae detachment from microalgae-Fe3O4 flocs was performed by addition of an anionic surfactant, sodium dodecyl sulfate (SDS). The detached CTAB-decorated Fe3O4 nanoparticles showed a steady reuse efficiency of about 80%. Furthermore, microalgae harvesting by CTAB-decorated Fe3O4 nanoparticles could contribute to a great improvement in the total extracted lipid content and greener wet extraction without the additional energy-intensive cell-disruption step, thus demonstrating the cell-disruption ability of CTAB-decorated Fe3O4 nanoparticles.</P>