ORCID Profile
0000-0002-7728-8888
Current Organisation
University College Dublin
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Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8GC03186J
Abstract: Incubating Nannochloropsis slurries in darkness at 38 °C activated auto-fermentation metabolism that thinned cell walls and led to increased cell rupture.
Publisher: Hindawi Limited
Date: 2010
DOI: 10.1155/2010/391632
Abstract: Chlorophyll is an essential compound in many everyday products. It is used not only as an additive in pharmaceutical and cosmetic products but also as a natural food colouring agent. Additionally, it has antioxidant and antimutagenic properties. This review discusses the process engineering of chlorophyll extraction from microalgae. Different chlorophyll extraction methods and chlorophyll purification techniques are evaluated. Our preliminary analysis suggests supercritical fluid extraction to be superior to organic solvent extraction. When compared to spectroscopic technique, high performance liquid chromatography was shown to be more accurate and sensitive for chlorophyll analysis. Finally, through CO 2 capture and wastewater treatment, microalgae cultivation process was shown to have strong potential for mitigation of environmental impacts.
Publisher: Elsevier BV
Date: 03-2012
Publisher: Elsevier BV
Date: 05-2012
DOI: 10.1016/J.BIOTECHADV.2012.01.001
Abstract: The rapid increase of CO(2) concentration in the atmosphere combined with depleted supplies of fossil fuels has led to an increased commercial interest in renewable fuels. Due to their high biomass productivity, rapid lipid accumulation, and ability to survive in saline water, microalgae have been identified as promising feedstocks for industrial-scale production of carbon-neutral biodiesel. This study examines the principles involved in lipid extraction from microalgal cells, a crucial downstream processing step in the production of microalgal biodiesel. We analyze the different technological options currently available for laboratory-scale microalgal lipid extraction, with a primary focus on the prospect of organic solvent and supercritical fluid extraction. The study also provides an assessment of recent breakthroughs in this rapidly developing field and reports on the suitability of microalgal lipid compositions for biodiesel conversion.
Publisher: Wiley
Date: 23-04-2012
DOI: 10.1002/JCTB.3821
Publisher: Wiley
Date: 09-11-2019
DOI: 10.1111/ANS.14827
Abstract: Current surgical practice often leads to excision of all papillary lesions of the breast diagnosed on percutaneous biopsy. This study aims to identify a subset of patients with papillary lesions who may be able to avoid surgery. Between January 2000 and December 2015, 157 cases of papillary lesions with complete surgical excision pathology results were reviewed retrospectively to compare the clinical, imaging and pathology features. Of these, 50 patients with benign papillary lesions without atypia and 19 patients with benign papillary lesions with atypia on needle biopsy were analysed to determine the rate of upgrade to malignancy after surgery. Of the 50 patients with benign papillary lesions without atypia on biopsy, two (4%) were upgraded to low grade ductal carcinoma in situ after surgical excision. Both these patients had suspicious features on imaging. Of the 19 patients with papillary lesions with atypia diagnosed on needle biopsy, eight (42%) were upgraded to malignancy after surgery. The differences between benign, atypical and malignant papillary lesions were further compared. Malignant lesions were more suspicious radiologically (P = 0.001), more likely to have architectural distortion (P = 0.001), more peripherally located (P = 0.001) and were larger in size (P = 0.01). Patients diagnosed with malignant lesions were also older (P = 0.001). Younger patients diagnosed with small central benign papillary lesions without atypia on needle biopsy, and without suspicious imaging, may be managed conservatively with surveillance.
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 04-2014
Publisher: Elsevier BV
Date: 2023
DOI: 10.1016/J.JBIOTEC.2022.11.011
Abstract: Acid-casein production generates waste streams that are rich in nitrogen (in the form of protein and nitrate) and phosphate. This makes this type of waste very difficult to treat using conventional techniques resulting in a high amount of operating cost and costly investment. In this research, the application of single culture or consortium of microalgae for uptake of nitrogen and phosphate in the wastewater of an acid-casein factory was investigated. The waste was a 1:1 mixture of nanofiltered whey permeate and dairy processing wastewater. Monocultures of Chlorella vulgaris, Tetradesmus obloquus, Nonnochlropsis ocenica and a consortium of the three microalgae were analyzed. The results showed that the consortium exhibited more efficient nitrogen and phosphate removal compared to the in idual species. The consortium was able to rapidly hydrolyse exogenous protein present in the waste medium, removing 88% of protein and breaking down complex protein molecules into simpler compounds (such as nitrate) for assimilation into the biomass. In the first fourteen days of cultivation, the rate of nitrate assimilation by the consortium biomass was lower than that of nitrate formation from protein degradation, leading to a net increase in nitrate concentration in the medium. As protein source was depleted and biomass concentration increased, however, the rate of nitrate assimilation began to exceed that of nitrate formation allowing for net removal of nitrate. The microalgae consortium was shown to successfully bioremediate all nitrates by day 21. It was indicated that Chlorella and Nannochloropsis species were responsible for nitrogen removal in monocultures. Phosphate, on the other hand, was efficiently removed by Tetradesmus. The results indicated that a consortium cultivation of three species of microalgae led to effective elimination of both nitrogen and phosphate. Combined flow-cytometry and microscopy analyses revealed that Chlorella overtook Tetradesmus and Nannochloropsis to emerge as the dominant population in the consortium by the end of the cultivation cycle. It can be concluded that the application of microalgae consortium for simultaneous recovery of nitrogen and phosphate is a promising approach for treating acid-casein wastewater.
Publisher: Springer International Publishing
Date: 2020
Publisher: Springer New York
Date: 07-06-2012
Publisher: Elsevier BV
Date: 02-2022
DOI: 10.1016/J.BIORTECH.2021.126597
Abstract: Novel cell-disruption combinations (autolytic incubation and hypotonic osmotic shock combined with HPH or pH12) were used to investigate the fundamental mass transfer of lipids and proteins from Nannochloropsis slurries (140 mg biomass/g slurry). Since neutral lipids exist as cytosolic globules, their mass transfer was directly dependent on disintegration of cell walls. Complete recovery was obtained with complete physical disruption. HPH combinations exerted more physical disruption and led to higher yields than pH12. In contrast, proteins exist as both cytosolic water-soluble fractions and cell-wall/membrane structural fractions and have a complex extraction behaviour. Mass transfer of cytosolic proteins was dependent on cell-wall disintegration, while that of structural proteins was governed by cell-wall disintegration and severance of protein linkage from the wall/membrane. HPH combinations exerted only physical disruption and were limited to releasing soluble proteins. pH12 combinations hydrolysed chemical linkages in addition to exerting physical disruption, releasing both soluble and structural proteins.
Publisher: Hindawi Limited
Date: 2015
DOI: 10.1155/2015/695061
Abstract: In the wake of global warming and rapid fossil fuel depletion, microalgae emerge as promising feedstocks for sustainable biofuel production. Nile red staining acts as a rapid diagnostic tool to measure the amount of biodiesel-convertible lipid that the cells accumulate. There is a need for the development of a more uniform staining procedure. In its first phase, this study examined the dependence of microalgal Nile red fluorescence ( Tetraselmis suecica ) in terms of its most pertinent staining variables. A quadratic surface model that successfully described the Nile red fluorescence intensity as a composite function of its variables was generated ( r 2 = 0.86 ). Cell concentration was shown to have a significant effect on the fluorescence intensity. Up to a certain threshold, fluorescence intensity was shown to increase with Nile red dye concentration. In its second phase, the study reviewed findings from previous Nile red studies to elucidate some of the fundamental mechanism underlying the diffusion of Nile red dye molecules into the microalgal cells and their subsequent interaction with intracellular lipids. Through the review process, we were able to develop a simple framework that provided a set of guidelines for the standardization of the Nile red staining procedure across different microalgal species.
Publisher: Elsevier BV
Date: 07-2018
DOI: 10.1016/J.BIORTECH.2018.03.129
Abstract: A single-step method for transesterifying and recovering lipids in concentrated slurries (ca 20% w/w solids) of ruptured microalgae is presented. A soluble Rhizomucor miehei lipase (RML) was used to directly transesterify the lipids in the marine microalgae Nannochloropsis salina. This allowed both triglycerides (TAG) and polar saponifiable lipids to be recovered as fatty acid methyl esters (FAME) using a nonpolar solvent (hexane). Up to 90 wt% of the total saponifiable lipids (SL) were converted to FAME within 24 h, approximately 75% of which was recovered in the hexane by centrifugation. Two pathways for the conversion and recovery of polar lipids were identified. The water in the slurry buffered against potential lipase inhibition by methanol, but necessitated a high methanol dose for maximal FAME conversion. Nonetheless the method enables the recovery of polar lipids as FAME while avoiding the need for both drying of the biomass and a downstream transesterification step.
Publisher: Elsevier BV
Date: 03-2021
Publisher: Springer New York
Date: 07-06-2013
Publisher: Elsevier BV
Date: 05-2021
Publisher: Elsevier BV
Date: 2011
DOI: 10.1016/J.BIORTECH.2010.06.136
Abstract: This study examines the performance of supercritical carbon dioxide (SCCO(2)) extraction and hexane extraction of lipids from marine Chlorococcum sp. for lab-scale biodiesel production. Even though the strain of Chlorococcum sp. used in this study had a low maximum lipid yield (7.1 wt% to dry biomass), the extracted lipid displayed a suitable fatty acid profile for biodiesel [C18:1 (∼63 wt%), C16:0 (∼19 wt%), C18:2 (∼4 wt%), C16:1 (∼4 wt%), and C18:0 (∼3 wt%)]. For SCCO(2) extraction, decreasing temperature and increasing pressure resulted in increased lipid yields. The mass transfer coefficient (k) for lipid extraction under supercritical conditions was found to increase with fluid dielectric constant as well as fluid density. For hexane extraction, continuous operation with a Soxhlet apparatus and inclusion of isopropanol as a co-solvent enhanced lipid yields. Hexane extraction from either dried microalgal powder or wet microalgal paste obtained comparable lipid yields.
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.BIORTECH.2019.121769
Abstract: Nitrogen-deprived Nannochloropsis cells invested their fixed carbon into the accumulation of triacylglycerol and cell wall cellulose (thickness of N-replete cell walls = 27.8 ± 5.8, N-deplete cell walls = 51.0 ± 10.2 nm). In this study, the effect of nitrogen depletion on the ability of the cells to weaken their own cell walls via autolysis was investigated. Autolytic cell wall thinning was achieved in both N-replete and N-deplete biomass by incubating highly concentrated slurries in darkness at 38 °C. The incubation forced cells to anaerobically ferment their intracellular cellulose and resulted in 30-40% reduction in cell wall thickness for both biomass types. This wall depletion weakened the cells and increased the extent of cell rupture by mechanical force (from 42 to 78% for N-replete biomass, from 36 to 62% for N-deplete biomass). Importantly, autolysis did not adversely impact the amino acid content of protein-rich N-replete biomass or the fatty acid content of lipid-rich N-deplete biomass.
No related grants have been discovered for RONALD HALIM.