Microalgae Chlorella as a Sustainable Feedstock …
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composition of the gas in the atmosphere (Ho et al. 2014; Ribeiro et al. 2014). In
addition, CO 2 released during the fermentation process for bioethanol production
can be recycled back for the use of microalgae cultivation. This can effectively minimize the amount of CO 2 being released into the atmosphere (Harun et al. 2010).
Regarding the living environment, microalgae are able to live in a variety of water
environment, which make the cultivation not dependent on arable land availability
(Hernández et al. 2015). Microalgae are highly specialized group of microorganisms
that are able to live in harsh conditions due to their unicellular or simple multicellular structures (Miranda et al. 2012). High degrees of environmental tolerance ensure
their easier isolation from the habitat (Ho et al. 2014).
So far, the potential of microalgae in biodiesel production has been acknowledged due to its high lipid content. As a matter of fact, the outstanding benefits that
offered by microalgae for bioethanol production mainly depend on its high carbohydrate content (Ho et al. 2013a, b). The exploitation of microalgae such as Chlorella,
Chlamydomonas, Porphyridium, Scenedesmus and Spirogyra has proven their capability as a potential feedstock for bioethanol production (Hernández et al. 2015). As
a comparison, Chlorella sp. is one step ahead than the others in its sustainability
as the growth rate is exceptionally fast and no controversial issues related to food
shortage (Lee et al. 2014). However, the major concern in the industry nowadays
is the commercial viability of the bioethanol production technologies. Hence, it is
important to employ the most effective and economical technology that can produce
high-quality bioethanol with lesser cost.
This research was set out to study the utilization of microalgae Chlorella sp. as
a sustainable feedstock for bioethanol production. The initial part of this research
started with the monitoring of Chlorella sp. growth rate to determine the most suitable period to harvest the microalgae cells. Under optimum or favourable growth
conditions, microalgae are believed to grow at an optimum rate, which leads to a
high rate of carbohydrate accumulation. Then, the main focus was directed for the
optimization of conversion technologies which were acid hydrolysis at the first stage
and followed by the optimization of bioethanol fermentation at the second stage.
2 Cultivation of Chlorella Species
Microalgae Chlorella sp. was kindly gifted by the Borneo Marine Research Institute
(BMRI) of Universiti Malaysia Sabah. Microalgae Chlorella sp. was cultivated in 1 L
conical flask with 10 replicates. Jaworski’s Medium (JM) was used for the cultivation
of Chlorella sp. The microalgae cultures were maintained at a temperature of 25–27
°C. The air was supplied throughout the cultivation process as shown in Fig. 1.
Microalgae growth was monitored and determined throughout the cultivation process. Approximately 20 ml of sample was taken once in three days for this analysis.
Microalgae cell concentration was estimated by measuring optical density at a wavelength of 750 nm (OD 750 ) using a calibrated UV/Vis spectrophotometer (Cecil CE
83
composition of the gas in the atmosphere (Ho et al. 2014; Ribeiro et al. 2014). In
addition, CO 2 released during the fermentation process for bioethanol production
can be recycled back for the use of microalgae cultivation. This can effectively minimize the amount of CO 2 being released into the atmosphere (Harun et al. 2010).
Regarding the living environment, microalgae are able to live in a variety of water
environment, which make the cultivation not dependent on arable land availability
(Hernández et al. 2015). Microalgae are highly specialized group of microorganisms
that are able to live in harsh conditions due to their unicellular or simple multicellular structures (Miranda et al. 2012). High degrees of environmental tolerance ensure
their easier isolation from the habitat (Ho et al. 2014).
So far, the potential of microalgae in biodiesel production has been acknowledged due to its high lipid content. As a matter of fact, the outstanding benefits that
offered by microalgae for bioethanol production mainly depend on its high carbohydrate content (Ho et al. 2013a, b). The exploitation of microalgae such as Chlorella,
Chlamydomonas, Porphyridium, Scenedesmus and Spirogyra has proven their capability as a potential feedstock for bioethanol production (Hernández et al. 2015). As
a comparison, Chlorella sp. is one step ahead than the others in its sustainability
as the growth rate is exceptionally fast and no controversial issues related to food
shortage (Lee et al. 2014). However, the major concern in the industry nowadays
is the commercial viability of the bioethanol production technologies. Hence, it is
important to employ the most effective and economical technology that can produce
high-quality bioethanol with lesser cost.
This research was set out to study the utilization of microalgae Chlorella sp. as
a sustainable feedstock for bioethanol production. The initial part of this research
started with the monitoring of Chlorella sp. growth rate to determine the most suitable period to harvest the microalgae cells. Under optimum or favourable growth
conditions, microalgae are believed to grow at an optimum rate, which leads to a
high rate of carbohydrate accumulation. Then, the main focus was directed for the
optimization of conversion technologies which were acid hydrolysis at the first stage
and followed by the optimization of bioethanol fermentation at the second stage.
2 Cultivation of Chlorella Species
Microalgae Chlorella sp. was kindly gifted by the Borneo Marine Research Institute
(BMRI) of Universiti Malaysia Sabah. Microalgae Chlorella sp. was cultivated in 1 L
conical flask with 10 replicates. Jaworski’s Medium (JM) was used for the cultivation
of Chlorella sp. The microalgae cultures were maintained at a temperature of 25–27
°C. The air was supplied throughout the cultivation process as shown in Fig. 1.
Microalgae growth was monitored and determined throughout the cultivation process. Approximately 20 ml of sample was taken once in three days for this analysis.
Microalgae cell concentration was estimated by measuring optical density at a wavelength of 750 nm (OD 750 ) using a calibrated UV/Vis spectrophotometer (Cecil CE