Abstract
This study evaluated the effectiveness of pressure-assisted ozonation (PAO) in Chlorella vulgaris (C. vulgaris) cell disruption, and compared the disruption result with that of the ultrasonication (US) by using four quantification indicators: cell counting, ultra violet (UV) absorbance, turbidity and visible light absorbance. It was found that under the condition of 0.8 MPa and 80 cycles, PAO treatment achieved cell rupture of 80.3%, with the power of 1080 W and treatment time of 60 min, US achieved cell rupture of 83.8%. Cell counting was a reliable indicator and applicable to both PAO and US treatments. Turbidity and visible light absorbance gave similar results and featured as the simplest operation. UV absorbance reflected the metabolite release due to cell breakage; however, it was less reproducible when it was applied to quantify the cell rupture by PAO. Its trend indicated that during cell disruption metabolite degradation occurred, especially after significant rupture in the case of excessive PAO treatment. The cellular morphology of C. vulgaris cells during PAO and US treatments was investigated by scanning electron microscope (SEM) which certified that the cells damage was caused by both physical and chemical attack.
Highlights
New energy from biomass has attracted more and more attention recently because of the low carbon emission, reproducible and environmentally friendly characteristics [1,2]
The cell disruption rate ranged between 0 and 100%, which was more applicable when cell count was used as the quantification method as the quantity of C. vulgaris cells could be measured absolutely before and after disruption, and in the case of complete disruption when all cells are disrupted, the minimum observed intact cell quantity is zero
The C. vulgaris cell disruption by conventional bubbling ozonation (CBO) without compression-decompression cycles was investigated and compared with that of pressure-assisted ozonation (PAO), and the results presented in Table 2 affirmed that the incorporating of moderate pressure effectively enhanced the cell disruption by ozonation
Summary
New energy from biomass has attracted more and more attention recently because of the low carbon emission, reproducible and environmentally friendly characteristics [1,2]. Chlorella vulgaris (C. vulgaris) is green eukaryotic microalgae and belongs to the family of Chlorellaceae and genus of Chlorella [3]. It is very commonly found in both fresh water and saline water. As the most crucial part of the microalgae utilization process, a feasible cell disruption technique is usually characterized by having the ability to continuously treat high-solids-content biomass, higher disruption rates, minimal damage to the integrity of target components and lower capital cost [12]. Since the quality of the target components is susceptible to different cell disruption methods applied, appropriate method should be carefully chosen depending on the utilization purpose
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