88
R. Abdulla et al.
Fig. 4 Effect of incubation
temperature on acid
hydrolysis
hydroxymethylfurfural (HMF). In their study, higher sulphuric acid concentration
showed lower concentration of glucose but a higher concentration of furfural and
HMF. The presence of organic acids, furfural and HMF affects the subsequent
fermentation process, delaying or inhibiting it (Miranda et al. 2012).
Nevertheless, some studies reported different results. Harun and Danquah (2011b)
reported that the amount of sugars released was decreasing with the increase of sulphuric acid concentration even at very low acid concentration. In their study, the
lowest sulphuric acid concentration performed (1% v/v) was proven to yield the
highest concentration of extracted glucose from microalgae Chlorococcum humocola. In contrast, Ho et al. (2013) reported that higher concentration of sulphuric
acid resulted in a higher concentration of extracted glucose. In their study, microalgae Scenedesmus obliquus biomass pretreated with 2.5% of sulphuric acid or higher
showed nearly 100% glucose yield.
3.2 Effect of Temperature on Acid Hydrolysis
The acid hydrolysis was carried out at different incubation temperatures, ranging
from 110 to 130 °C with 5 °C increment, while sulphuric acid concentration (2.0 M)
and incubation time (30 min) were kept constant. Figure 1.4 shows the relationship
between the incubation temperature and the concentration of glucose. According to
Fig. 1.4, higher temperature resulted in a higher concentration of extracted glucose
as an increasing trend was observed. Highest peak was obtained at 130 °C with a
concentration of glucose of 5.382 ± 0.063 g/l. The lowest peak can be observed when
110 and 115 °C were used which had a glucose concentration of 1.604 ± 0.036 g/l.
In this study, the highest concentration of extracted glucose (5.382 ± 0.063 g/l)
was found to be achieved with the incubation temperature of 130 °C. However,
different studies had reported different optimum temperatures or temperature ranges
R. Abdulla et al.
Fig. 4 Effect of incubation
temperature on acid
hydrolysis
hydroxymethylfurfural (HMF). In their study, higher sulphuric acid concentration
showed lower concentration of glucose but a higher concentration of furfural and
HMF. The presence of organic acids, furfural and HMF affects the subsequent
fermentation process, delaying or inhibiting it (Miranda et al. 2012).
Nevertheless, some studies reported different results. Harun and Danquah (2011b)
reported that the amount of sugars released was decreasing with the increase of sulphuric acid concentration even at very low acid concentration. In their study, the
lowest sulphuric acid concentration performed (1% v/v) was proven to yield the
highest concentration of extracted glucose from microalgae Chlorococcum humocola. In contrast, Ho et al. (2013) reported that higher concentration of sulphuric
acid resulted in a higher concentration of extracted glucose. In their study, microalgae Scenedesmus obliquus biomass pretreated with 2.5% of sulphuric acid or higher
showed nearly 100% glucose yield.
3.2 Effect of Temperature on Acid Hydrolysis
The acid hydrolysis was carried out at different incubation temperatures, ranging
from 110 to 130 °C with 5 °C increment, while sulphuric acid concentration (2.0 M)
and incubation time (30 min) were kept constant. Figure 1.4 shows the relationship
between the incubation temperature and the concentration of glucose. According to
Fig. 1.4, higher temperature resulted in a higher concentration of extracted glucose
as an increasing trend was observed. Highest peak was obtained at 130 °C with a
concentration of glucose of 5.382 ± 0.063 g/l. The lowest peak can be observed when
110 and 115 °C were used which had a glucose concentration of 1.604 ± 0.036 g/l.
In this study, the highest concentration of extracted glucose (5.382 ± 0.063 g/l)
was found to be achieved with the incubation temperature of 130 °C. However,
different studies had reported different optimum temperatures or temperature ranges