Development of an eco-friendly agar extraction technique from the red seaweed Gracilaria lemaneiformis

Li, Haiyan; Yu, Xingju; Jin, Yan; Zhang, Wei; Liu, Yuanling

doi:10.1016/j.biortech.2007.07.002

Cited by 99 publications

(48 citation statements)

References 17 publications

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“…1, Table 2). Either of these two gel parameters has been regarded as the metric for agar gel quality (e.g., Mrani et al 1995;Norziah et al 2006;Prasad et al 2007;Li et al 2008). Lowest gel qualities were obtained at 0% alkali concentration in all pretreatment durations (regarded as native extracts).…”

Section: Resultsmentioning

confidence: 99%

Production and properties of agar from the invasive marine alga, Gracilaria vermiculophylla (Gracilariales, Rhodophyta)

et al. 2009

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The utilization potential, in terms of agar production, of the invasive alga, Gracilaria vermiculophylla, collected at Ria de Aveiro, northwestern Portugal was investigated. The agar yield ranged from 15% to 33%, with pre-extraction treatment with alkali generally increasing the yield. The gel quality (gel strength and apparent Young's modulus) was best (>600 g cm −2 and >1,000 kPa, respectively) when alkali treatment with 6% NaOH for 3.5 h was performed. At these pretreatment conditions, the effect of extraction time was also investigated and highest yield and best gel quality were obtained with a 2 h extraction time. By employing these extraction conditions, G. vermiculophylla can be a source of industrial food-grade agar. The structure of agar from G. vermiculophylla was determined through chemical techniques and FTIR and NMR spectrometry. It is mainly composed of alternating 3-linked D-galactose and 4-linked 3,6-anhydro-L-galactose, with methyl substitution occurring at 16-19 mol% of C-6 in 3-linked units and 2-3 mol% of C-2 in 4-linked units. A minor sulfation on C-4 of 3-linked units was also detected; while precursor units (6-sulfated 4-linked galactosyl moieties) were found in the native extract.

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Section: Resultsmentioning

confidence: 99%

Production and properties of agar from the invasive marine alga, Gracilaria vermiculophylla (Gracilariales, Rhodophyta)

et al. 2009

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“…The 5% NaOH concentration was optimal for alkali modification for this technique. The duration of photobleaching had a significant impact on agar gel strength; the optimal photobleaching duration was 5 h. It may be that agar with repeating sulfate-connected disaccharides underwent photolysis with the free radicals during the photobleaching process in water, which improved the gel strength and led to a fairly modest decrease in total sulfate and increase in 3,6-AG levels (Li et al 2008). Algal length had some impact on agar yield, but not on agar quality.…”

Section: Discussionmentioning

confidence: 97%

Optimization and scale-up of a new photobleaching agar extraction process from Gracilaria lemaneiformis

Huang

Xin

et al. 2008

J Appl Phycol

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An eco-friendly photobleaching extraction process for agar extraction from the red alga Gracilaria lemaneiformis was developed for the benefit of workers' health and environmental safety. Here we report the optimization of key process parameters (alkali modification concentration, photobleaching duration, algal length and screen filter opening size) in order to scale up this new technique. The optimal conditions were found to be modification by 3-5% NaOH, photobleaching for 5 h, using algal fragments 2-4 cm in length, and a filter screen with a 6 μm opening. A 20-L agar extraction reactor was thus constructed, and the scale-up of the agar extraction process was tested in six batch experiments. The resulting agar quality was similar to that of the laboratory-scale extraction. In addition, batch-to-batch reproducibility was excellent. The results demonstrate the excellent scale-up ability and potential application of this new photobleaching agar extraction process on a commercial scale. The agar yield and gel strength for 5% NaOH modified agar were 26.8% and 1,897 g cm −2 , while those for 3% NaOH modified agar were 28.2% and 1,287 g cm −2 , respectively.It is clear that the agar yield and quality can be manipulated via alkali modification in this new eco-friendly extraction to meet market demands.

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“…This colour variation issue was usually controlled through chemical bleaching process. This process not only less eco-friendly, but also lead to reduction of extraction yield and quality due to difficulties of controlling the pH and solvent concentrations during the bleaching stage [9,10,129,130]. Thus, an ecofriendly bleaching process which adopted 'green energy' of sunlight has been developed.…”

Section: Photo-bleaching Extraction Processmentioning

confidence: 99%

“…This green method has shown a huge potential for the production of high quality and eco-friendly seaweed hydrocolloids. It not only eliminates the usage of harmful chemicals but at the same time improves the rheological properties (gel strength, gelling temperature, sulfate content, 3,6-anhydro-L-galactose content) of agar compared to native, alkali-modified and chemical-bleached agar under optimum photo-bleaching duration of 5 hours [129,130]. The equipment cost maybe a drawback for this method, which requires further study.…”

Section: Photo-bleaching Extraction Processmentioning

confidence: 99%

“…But excessive buffering required during extraction made it costly and less economic [134][135][136]. Both photo-bleaching and reaction extraction has shown some potential in improving the extraction qualities of seaweed hydrocolloids based on some previous studies [126,[128][129][130], but their limitations still remained unclear. High capital cost might be a drawback for mass extraction of seaweed hydrocolloids using these methods.…”

Section: Advantages and Limitations Regardingmentioning

confidence: 99%

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A review of extractions of seaweed hydrocolloids: Properties and applications

Khalil¹,

Lai²,

Tye³

et al. 2018

Express Polym. Lett.

133

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Development of an eco-friendly agar extraction technique from the red seaweed Gracilaria lemaneiformis

Cited by 99 publications

References 17 publications

Production and properties of agar from the invasive marine alga, Gracilaria vermiculophylla (Gracilariales, Rhodophyta)

Production and properties of agar from the invasive marine alga, Gracilaria vermiculophylla (Gracilariales, Rhodophyta)

Optimization and scale-up of a new photobleaching agar extraction process from Gracilaria lemaneiformis

A review of extractions of seaweed hydrocolloids: Properties and applications

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