Natural production of alkane by an easily harvested freshwater cyanobacterium, Phormidium autumnale KNUA026

Abstract

A freshwater cyanobacterium, Phormidium autumnale KNUA026, was isolated from puddles of icy water in Gyeongsan City, South Korea and its potential as a biofuel feedstock was investigated. Maximal growth was obtained when the culture was incubated at 25°C and around pH 9.0. The total lipid content of the isolate was approximately 14.0% of dry weight and it was found that strain KNUA026 was able to autotrophically synthesize heptadecane (C 17 H 36 ) which can be directly used as fuel without requiring a transesterification step. As this benthic cyanobacterium was capable of forming thick mats, it could be easily harvested by gravitational settling and this property may reduce the cost of production in commercial applications. Hence, P. autumnale KNUA026 appears to be a promising resource for use in the production of microalgae-based biofuels.Key Words: algae-based fuel; alkane; cyanobacterium; heptadecane; Phormidium autumnale INTRODUCTIONIn recognition of the current energy crisis, alternative energy sources are currently being explored and developed at an increasing pace; biofuels in particular have received a considerable amount of attention over the past few years. Conventional biofuels, such as bioethanol and biodiesel, are produced primarily from cereal crops and oil seeds. However, the mass production of crop-based biofuels has resulted in serious side effects, such as increases in food prices, deforestation, and carbon emissions (Sims et al. 2010). Thus, algae-based biofuels have been recognized as an attractive option, as they use minimal land resources (Chisti 2007) and do not compete with food production (Huang et al. 2010). Additionally, algaebased biofuels have several other advantages, including rapid growth rates (Schenk et al. 2008), higher lipid contents (Hu et al. 2008), and higher CO 2 uptake rates (Jorquera et al. 2010) relative to other energy crops. Considering these advantages, microalgae biofuels have been recognized as the only current renewable source of liquid transportation fuel which is compatible with the existing engines and distribution systems (Schenk et al. 2008). Microalgae, including cyanobacteria, have been reported to generate a variety of lipids, hydrocarbons, fatty alcohols, and other complex oils ( ), until growth was apparent. An aliquot of the brown-colored biomass was taken by pipetting, and was sonicated for approximately 3-5 s using an ultrasonic cell disruptor (Model 550; Fisher Scientific, Pittsburgh, PA, USA). The filaments were then transferred onto BG-11 agar plates containing 100 µg mL -1 of meropenem (Yuhan Pharmaceuticals, Ochang, Korea) and were incubated in the dark for 24 h to eliminate contaminating bacteria (Choi et al. 2008). The culture was then inoculated onto fresh BG-11 agar plates and incubated for 14 days under a light : dark cycle (16 : 8 h) at 15°C. Morphological and molecular identificationThe isolate was grown in BG-11(+) medium for 21 days. Live cells were harvested by centrifugation at 3,000 ×g for 5 min, washed with sterile distilled water, ...

Comparative growth characteristics and interspecific competitive interaction of two cyanobacteria, Phormidium autumnale and Nostoc sp.

“…Phormidium autumnale KNUA026 and Nostoc sp. grew well in a wide range of pH (i.e., pH 6–12) (Chang et al., 2013; Hong et al., 2018). Alkalization of BG‐11 media increased the CA activity of P. autumnale and Nostoc sp.…”

Characterization of fatty acid components from Tetradesmus obliquus KNUA019 (Chlorophyta, Scenedesmaceae) for a resource of biofuel production

“…1a, left panel); and light microscopy ( Fig. 1a, lower panel) based on previous work by Chang et al (2013). Growth rate was highest at 25 °C (Fig.…”

“…The culture was then inoculated onto fresh BG-11(+) agar plates and incubated for 14 days under a light:dark cycle (16:8 h) at 15 °C. This experiment has been carried out with minor modifications in previous studies (Chang et al 2013). Live cells were harvested by centrifugation at 4000 rpm for 10 min, washed with sterile distilled water, and visualized at 400 × using a Zeiss Axioskop 2 light microscope (Carl Zeiss, Standort Gottingen, Vertrieb, Germany) equipped with differential interference contrast optics.…”

Characterization of Chlorella sorokiniana and Chlorella vulgaris fatty acid components under a wide range of light intensity and growth temperature for their use as biological resources

“…The aseptic isolation of microalgae from a mixed culture with bacteria was performed by spreading or streaking on a BG-11 culture medium ( Chang et al., 2013 ). The C. sorokiniana strains KNUA114 and KNUA122, as well as the C. vulgaris strain KNUA104, all lacked a flagellum, a common feature of species belonging to the genus Chlorellaceae ( Figure 1 C-E).…”

“…Furthermore, the fatty acid components of C. sorokiniana KNUA114 and KNUA122 strains were incomparable with those of the C. vulgaris KNUA104 strain, as the growth of the latter was inhibited at high temperatures ( Figure 4 C, Table 1 ). Previous research has described saturated fatty acids (SFAs) as biological resources for biofuel production ( Chang et al., 2013 ; Yong et al., 2019 ). These fatty acid components are commonly found in microalgae ( Hong et al., 2016 ), which may be used as a potential source for these valuable compounds ( Ötleş and Pire, 2001 ; Alberts, 2003 ; Herrero et al., 2006 ; Spolaore et al., 2006 ; Knothe, 2008 ; Mohammady, 2011 ).…”