Armando T. Quitain

Supercritical Carbon Dioxide Extraction of Fucoxanthin from Undaria pinnatifida

Undaria pinnatifida, commonly known as wakame in Japan, is one species of brown seaweeds containing valuable bioactive organic compounds such as fucoxanthin, a carotenoid, which has numerous functional properties. However, most of the seaweeds that do not meet strict quality standards are normally discarded as wastes or returned to the sea, a situation which is becoming an environmental concern. In this research, supercritical carbon dioxide (SCCO₂) extraction was investigated for the isolation of fucoxanthin. SCCO₂ extraction experiments were carried out at temperature range of 25-60 °C and pressure range of 20-40 MPa, at a carbon dioxide flow rate of 1.0-4.0 mL/min. Results showed that fucoxanthin recovery closed to 80% could be obtained at 40 °C and 40 MPa in extraction time of 180 min. The recovery increased with decreasing temperature and increasing pressure. Pretreatment with microwave (MW) also enhanced the efficiency of extraction due most likely to disruption of the cell membrane. Application of SCCO₂, generally regarded as safe and environmentally benign solvent, for extraction of useful bioactive compounds from unwanted or substandard seaweeds look promising in the near future. The extracts obtained using the method can be utilized as food and pharmaceutical additive, and can be used in the development of new health supplements.

Characterization of natural low transition temperature mixtures (LTTMs): Green solvents for biomass delignification

The aim of this work was to characterize the natural low transition temperature mixtures (LTTMs) as promising green solvents for biomass pretreatment with the critical characteristics of cheap, biodegradable and renewable, which overcome the limitations of ionic liquids (ILs). The LTTMs were derived from inexpensive commercially available hydrogen bond acceptor (HBA) and l-malic acid as the hydrogen bond donor (HBD) in distinct molar ratios of starting materials and water. The peaks involved in the H-bonding shifted and became broader for the OH groups. The thermal properties of the LTTMs were not affected by water while the biopolymers solubility capacity of LTTMs was improved with the increased molar ratio of water and treatment temperature. The pretreatment of oil palm biomass was consistence with the screening on solubility of biopolymers. This work provides a cost-effective alternative to utilize microwave hydrothermal extracted green solvents such as malic acid from natural fruits and plants.

Polyphenolic Contents and Antioxidant Activities of Lawsonia Inermis Leaf Extracts Obtained by Microwave-assisted Hydrothermal Method

Abstract Extracts obtained by microwave-assisted hydrothermal extraction of Lawsonia inermis leaves were evaluated for the presence of polyphenolic compounds and antioxidant activities. Extraction experiments were performed in temperature-controlled mode at a range of 100 to 200oC, and extraction time of 5 to 30 min, and microwave-controlled mode at a power from 300–700 W, in irradiation time of 30 to 120 s. Polyphenolic contents were measured using Folin-Ciocalteau method, while antioxidant properties were analyzed using DPPH radical scavenging activities (RSA) expressed in BHA equivalents. Results showed that best values of RSA were obtained at mild temperature range of 100–120 °C. Controlling microwave power at short irradiation time gave better results than temperature-controlled treatment as well. Furthermore, comparison with the result obtained at room temperature confirmed that the use of microwave was more effective for extracting polar components that normally possess higher antioxidant activities.

Synergizing graphene oxide with microwave irradiation for efficient cellulose depolymerization into glucose

The abundance in hydroxyl groups neighboring the hydrolytic site (β-1,4 glycosidic bonds) in cellulose forms a tightly packed crystalline structure, and hence, is a major challenge in cellulose depolymerization into fermentable sugars. Herein, we report on the synergistic effect of the carbocatalyst, graphene oxide (GO) and microwave irradiation (MW) on cellulose depolymerization in the absence of pretreatment. Results showed that microcrystalline cellulose (MCC) can be effectively depolymerized into glucose in as short as 30 s at 473 K (800 W). Generated yields without pretreatments were as high as 61 ± 4% within 60 min (200 W and 453 K), which has never been reported before to the best of our knowledge. The synergy of GO and MW was demonstrated by high heating rates and which allowed for the activation of in situ crystalline-to-amorphous transformations and suppressed immediate formation of degradation products. The activity of GO under MW was much higher than those of other solid acid catalysts such as Amberlyst 15, sulfated zirconia, and phosphotungstic acid due to the variety of surface functionalities and its high microwave absorptivity. The depolymerization mechanism was also discussed in terms of surface attrition of MCC as observed via scanning electron microscopy. On this basis, the proposed process offers an important strategy for cellulose depolymerization.

Choline chloride (ChCl) and monosodium glutamate (MSG)-based green solvents from optimized cactus malic acid for biomass delignification

This work aimed to develop an efficient microwave-hydrothermal (MH) extraction of malic acid from abundant natural cactus as hydrogen bond donor (HBD) whereby the concentration was optimized using response surface methodology. The ideal process conditions were found to be at a solvent-to-feed ratio of 0.008, 120°C and 20min with 1.0g of oxidant, H2O2. Next generation environment-friendly solvents, low transition temperature mixtures (LTTMs) were synthesized from cactus malic acid with choline chloride (ChCl) and monosodium glutamate (MSG) as hydrogen bond acceptors (HBAs). The hydrogen-bonding interactions between the starting materials were determined. The efficiency of the LTTMs in removing lignin from oil palm biomass residues, empty fruit bunch (EFB) was also evaluated. The removal of amorphous hemicellulose and lignin after the pretreatment process resulted in an enhanced digestibility and thermal degradability of biomass.

Supercritical CO2 extraction of essential oil from Kabosu (Citrus sphaerocarpa Tanaka) peel

BackgroundCitrus sphaerocarpa Hort. ex Tanaka is one of many popular sour citruses in Japan. Its juice processing peel residues contain a lot of useful compounds including essential oil. Our interests mainly focused on the extraction of this essential oil using supercritical carbon dioxide (SC-CO2), an environmentally benign and generally regarded as safe solvent that has many advantages such as low critical temperature, low viscosity, and easy separation from the extract. In this research, essential oil was extracted from Citrus sphaerocarpa Tanaka peel using SC-CO2 at extraction temperatures of 313 to 353 K and pressures of 10 to 30 MPa.ResultsA maximum yield of 1.55% (by weight of wet sample) was obtained at the temperature of 353 K and the pressure of 20 MPa. The yield obtained by SC-CO2 method was over 13 times higher than that of the conventional cold-press method. Extracted essential oil was qualitatively analyzed using GC/MS, identifying 49 compounds including several non-polar and weakly polar hydrocarbons such as terpenoid, free fatty acid, and coumarin. Compared to the extracts obtained by the conventional methods, the extracts by SC-CO2 had lower content of monoterpenes and higher content of oxygenated compounds, sesquiterpenes, which strongly contribute to the aromatic characteristics of the extracts. Auraptene, a bioactive compound was also identified in the SC-CO2 extract.ConclusionsKabosu essential oil with a fresh natural fragrance was effectively extracted using SC-CO2 compared to the conventional extraction method. In addition, it was found that the extract contained higher content of aromatic components that characterize Kabosu. This work provides an important sequential method for the recovery of valuable compounds from citrus fruit waste using an environmentally friendly technique.

Microwave-Based Pretreatment for Efficient Biomass-to-Biofuel Conversion

Pretreatment has been considered an important step for efficient and effective biomass-to-biofuel conversion. One of many promising methods of pretreatment includes the use of microwave (MW). MW-based pretreatment approach utilizes both thermal and non-thermal effects generated by an extensive intermolecular collision as a result of realignment of polar molecules with MW oscillations. Compared to conventional heating, electromagnetic field generated by MW has the ability to directly interact with the material to produce heat, thereby accelerating chemical, physical, and biological processes. The advantages of employing MW rather than the conventional heating include reduction of process energy requirements, selective processing, and capability for instantaneous start and ceasing of a process. This also offers enormous benefits such as energy efficiency due to rapid and selective heating, and the possibility for developing a compact process.

Extraction of Bioactive Compounds from Leaves of Lawsonia inermis by Green Pressurized Fluids

Supercritical carbon dioxide and microwave-assisted hydrothermal methods were investigated for extraction of bioactive components of leaves of Lawsonia inermis (henna), a world renowned source of natural hair dye component called lawsone (2-hydroxy-1,4-naphthoquinone). Results showed that the use of supercritical carbon dioxide was selective to extraction of non-polar compounds such as essential oils, and the recovery of lawsone was low. However, using hot and compressed water as a solvent, a maximum recovery of lawsone of about 76.2% could be obtained at 120°C and extraction time of 30 min. At higher temperatures and longer treatment time, the yield and recovery decreased due most likely to the degradation of the target compounds at severe conditions. Moreover, the highest composition of lawsone close to 24% was obtained at microwave power of 600 W in irradiation time of 1 min. Mild hydrothermal conditions assisted with microwave heating are recommended in order to obtain high recovery of lawsone. Direct microwave heating of the polar components and solvent could lead to rapid extraction of the target compounds.

Thermogravimetric analysis and kinetic modeling of low-transition-temperature mixtures pretreated oil palm empty fruit bunch for possible maximum yield of pyrolysis oil

The impacts of low-transition-temperature mixtures (LTTMs) pretreatment on thermal decomposition and kinetics of empty fruit bunch (EFB) were investigated by thermogravimetric analysis. EFB was pretreated with the LTTMs under different duration of pretreatment which enabled various degrees of alteration to their structure. The TG-DTG curves showed that LTTMs pretreatment on EFB shifted the temperature and rate of decomposition to higher values. The EFB pretreated with sucrose and choline chloride-based LTTMs had attained the highest mass loss of volatile matter (78.69% and 75.71%) after 18 h of pretreatment. For monosodium glutamate-based LTTMs, the 24 h pretreated EFB had achieved the maximum mass loss (76.1%). Based on the Coats-Redfern integral method, the LTTMs pretreatment led to an increase in activation energy of the thermal decomposition of EFB from 80.00 to 82.82-94.80 kJ/mol. The activation energy was mainly affected by the demineralization and alteration in cellulose crystallinity after LTTMs pretreatment.

Synthesis and characterization of hybrid composite aerogels from alginic acid and graphene oxide

Aerogels are one class of solid adsorbents that are gaining considerable attention because of their very high porosity, high specific surface area, and extremely low density. However, most aerogels being studied and used recently are synthetic in nature, which are usually mesoporous silica and metal-organic frameworks (MOFs). As research focus is geared towards sustainable engineering, it is desired to utilize biomass to synthesize aerogels. This study thus aims to produce alginic acid-graphene oxide hybrid composite aerogels and compare them with its existing synthetic counterparts. Alginic acid (AA) is an abundant marine biopolymer that easily forms gels, while graphene oxide (GO) is a nanomaterial consisting of many functional groups. Aerogels made up of AA and GO were successfully synthesized using a sol-gel method. The hydrogel was converted into an aerogel by drying with supercritical carbon dioxide. The percentage of graphene oxide was varied from 0 to 20%. The aerogels were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and nitrogen adsorption–desorption measurements. The addition of GO increased the specific surface area of the aerogel up to a certain point, after which it decreased. The 10% GO-AA aerogel showed the most favourable porosity characteristics with a specific surface area of 177.26 m2/g and average pore diameter of 53.2 nm. There had been no observable difference in the thermal behaviour of the aerogels with a change in the concentration of graphene oxide.