Mild pressure induces rapid accumulation of neutral lipid (triacylglycerol) in Chlorella spp.

Effective enhancement of neutral lipid (especially triacylglycerol, TAG) content in microalgae is an important issue for commercialization of microalgal biorefineries. Pressure is a key physical factor affecting the morphological, physiological, and biochemical behaviors of organisms. In this paper, we report a new stress-based method for induction of TAG accumulation in microalgae (specifically, Chlorella sp. KR-1 and Ch. sp. AG20150) by very-short-duration application of mild pressure. Pressure treatments of 10-15bar for 2h resulted in a considerable, ∼55% improvement of the 10-100g/Lcells' TAG contents compared with the untreated control. The post-pressure-treatment increase of cytoplasmic TAG granules was further confirmed by transmission electron microscopy (TEM). Notwithstanding the increased TAG content, the total lipid content was not changed by pressurization, implying that pressure stress possibly induces rapid remodeling/transformation of algal lipids rather than de novo biosynthesis of TAG.

[1]  R. Wijffels,et al.  An Outlook on Microalgal Biofuels , 2010, Science.

[2]  E. Delong,et al.  Adaptation of the membrane lipids of a deep-sea bacterium to changes in hydrostatic pressure. , 1985, Science.

[3]  Youngsook Lee,et al.  The small molecule fenpropimorph rapidly converts chloroplast membrane lipids to triacylglycerols in Chlamydomonas reinhardtii , 2015, Front. Microbiol..

[4]  Y. Li-Beisson,et al.  Lipids: From Chemical Structures, Biosynthesis, and Analyses to Industrial Applications. , 2016, Sub-cellular biochemistry.

[5]  Y. Oh,et al.  Cell-wall disruption and lipid/astaxanthin extraction from microalgae: Chlorella and Haematococcus. , 2016, Bioresource technology.

[6]  Young-Chul Lee,et al.  Magnesium aminoclay enhances lipid production of mixotrophic Chlorella sp. KR-1 while reducing bacterial populations. , 2016, Bioresource technology.

[7]  K. Bišová,et al.  Accumulation of energy reserves in algae: From cell cycles to biotechnological applications. , 2015, Biotechnology advances.

[8]  S. Merchant,et al.  TAG, you're it! Chlamydomonas as a reference organism for understanding algal triacylglycerol accumulation. , 2012, Current opinion in biotechnology.

[9]  G. Demazeau,et al.  Development of high hydrostatic pressure in biosciences: pressure effect on biological structures and potential applications in biotechnologies. , 2010, Biotechnology advances.

[10]  Y. Li-Beisson,et al.  Rapid Induction of Lipid Droplets in Chlamydomonas reinhardtii and Chlorella vulgaris by Brefeldin A , 2013, PloS one.

[11]  V. Zachleder,et al.  Oil Overproduction by Means of Microalgae , 2014 .

[12]  Pierre-Alexandre Vidi,et al.  Plastoglobule lipid bodies: their functions in chloroplasts and their potential for applications. , 2007, Advances in biochemical engineering/biotechnology.

[13]  Moon-Hee Choi,et al.  Aminoclay-conjugated TiO2 synthesis for simultaneous harvesting and wet-disruption of oleaginous Chlorella sp. , 2014 .

[14]  Gilles Peltier,et al.  Microalgal lipid droplets: composition, diversity, biogenesis and functions , 2014, Plant Cell Reports.

[15]  P. Shrestha,et al.  Mobilization of arachidonyl moieties from triacylglycerols into chloroplastic lipids following recovery from nitrogen starvation of the microalga Parietochloris incisa. , 2005, Biochimica et biophysica acta.

[16]  Eunji Choi,et al.  Improved biomass and lipid production in a mixotrophic culture of Chlorella sp. KR-1 with addition of coal-fired flue-gas. , 2014, Bioresource technology.

[17]  Poonam Singh,et al.  Trends and novel strategies for enhancing lipid accumulation and quality in microalgae , 2016 .

[18]  Young-Chul Lee,et al.  Recent nanoparticle engineering advances in microalgal cultivation and harvesting processes of biodiesel production: a review. , 2015, Bioresource technology.

[19]  P. Mañas,et al.  Morphological and Physiological Changes Induced by High Hydrostatic Pressure in Exponential- and Stationary-Phase Cells of Escherichia coli: Relationship with Cell Death , 2004, Applied and Environmental Microbiology.

[20]  Y. Oh,et al.  Downstream integration of microalgae harvesting and cell disruption by means of cationic surfactant-decorated Fe3O4 nanoparticles , 2016 .

[21]  C. Pascual,et al.  Variation in Resistance to High Hydrostatic Pressure andrpoS Heterogeneity in Natural Isolates ofEscherichia coli O157:H7 , 2001, Applied and Environmental Microbiology.

[22]  J. Seckbach.  Pigmentation of Algae under Pressure1 , 1971 .

[23]  Eunji Choi,et al.  Mixotrophic cultivation of oleaginous Chlorella sp. KR-1 mediated by actual coal-fired flue gas for biodiesel production , 2014, Bioprocess and Biosystems Engineering.

[24]  Q. Hu,et al.  Microalgal triacylglycerols as feedstocks for biofuel production: perspectives and advances. , 2008, The Plant journal : for cell and molecular biology.