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Microalgal lipids are promising and sustainable sources for the production of third-generation biofuels, foods, and medicines. A high lipid yield during the extraction process in microalgae could be influenced by the suitable pretreatment and lipid extraction methods. The extraction method itself could be attributed to the economic and environmental impacts on the industry. This review summarizes the pretreatment methods including mechanical and non-mechanical techniques for cell lysis strategy before lipid extraction in microalgae biomass. The multiple strategies to achieve high lipid yields via cell disruption techniques are discussed. These strategies include mechanical (shear forces, pulse electric forces, waves, and temperature shock) and non-mechanical (chemicals, osmotic pressure, and biological) methods. At present, two techniques of the pretreatment method can be combined to increase lipid extraction from microalgae. Therefore, the extraction strategy for a large-scale application could be further strengthened to optimize lipid recovery by microalgae. [ABSTRACT FROM AUTHOR]

This document, titled "Agronomy 12," is a research article that focuses on sustainable waste management in agriculture and livestock industries. It emphasizes the importance of composting as a natural process that converts organic waste into nutrient-rich compost, which can enhance soil health and fertility. The article discusses the benefits of composting, such as reducing the need for chemical fertilizers and mitigating climate change by sequestering carbon in the soil. It also acknowledges the challenges and disadvantages of composting, including the need for proper management to prevent contamination and the presence of potentially harmful elements. Additionally, the article explores alternative methods of waste utilization, such as using waste materials for mushroom cultivation. Overall, this scholarly article provides valuable insights into sustainable agriculture and food systems and can be a helpful resource for library patrons conducting research in this field. [Extracted from the article]

The use of chitosan as a flocculant has become a topic of interest over the years due to its positively charged polymer and biodegradable and non-toxic properties. However, most studies only focus on microalgae and wastewater treatment. This study provides crucial insight into the potential of using chitosan as an organic flocculant to harvest lipids and docosahexaenoic acid (DHA-rich Aurantiochytrium sp. SW1 cells by examining the correlation of flocculation parameters (chitosan concentration, molecular weight, medium pH, culture age, and cell density) toward the flocculation efficiency and zeta potential of the cells. A strong correlation between the pH and harvesting efficiency was observed as the pH increased from 3, with the optimal flocculation efficiency of >95% achieved at a chitosan concentration of 0.5 g/L at pH 6 where the zeta potential was almost zero (3.26 mV). The culture age and chitosan molecular weight have no effect on the flocculation efficiency but increasing the cell density decreases the flocculation efficiency. This is the first study to reveal the potential of chitosan to be used as a harvesting alternative for thraustochytrid cells. [ABSTRACT FROM AUTHOR]

Microalgae represent promising sources of bioactive compounds for pharmaceutical and industrial applications. The emergence of antibiotic resistant bacteria leads to the need to explore new cost-effective, safe, and potent bioactive compounds from the microalgae. This study aimed to investigate the potential of local microalgae for their antimicrobial properties and bioactive compounds. Three local microalgae namely Chlorella sorokiniana (UKM2), Chlorella sp. UKM8, and Scenedesmus sp. UKM9 biomass methanol extracts (ME) were prepared and tested against Gram-positive and Gram-negative bacteria. Chlorella sp. UKM8-ME showed the highest antibacterial activity. UKM8-ME minimum inhibitory concentrations were in the range of 0.312 to 6.25 mg/mL. Cytotoxicity evaluation using MTT assay showed that the microalgae methanolic extracts did not exhibit cytotoxicity against Vero-cells. The UKM8-ME was mainly containing 28 compounds from the Gas Chromatography-Mass Spectrometry (GC–MS) analysis. Major compounds of UKM8-ME included phenol (18.5%), hexadecanoic acid (18.25%), phytol (14.43%), 9,12-octadecadienoic acid (13.69%), and bicyclo[3.1.1]heptane (7.23%), which have been previously described to possess antimicrobial activity. Hence, Chlorella sp. (UKM8) methanol extracts showed promising antibacterial activity. More comprehensive studies are required to purify these antimicrobial compounds and develop our understanding on their mechanism in UKM8-ME to unleash their specific potential. [ABSTRACT FROM AUTHOR]

Summary: The low cost, low over‐potential loss, good catalytic properties for hydrogen evolution reaction (HER), high corrosion stability, commercially available, and could be applied in pH‐neutral solution and ambient temperature are important properties for the cathode materials when it is applied in microbial electrolysis cell (MEC) technology. This study has two‐pronged objectives: the first is to investigate the feasibility of titanium (Ti) and graphite felt (GF) coated with nickel (Ni), and the second is to generate hydrogen from the fermentation effluent (FE). The electrodeposition (ED) method was used to deposit Ni catalyst onto Ti (Ni/Ti) and GF (Ni/GF) surfaces. The scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) spectroscopy were used to characterize the cathode morphology and element composition. The catalytic properties of Ni/Ti and Ni/GF could be evaluated using the linear sweep voltammetry tests. The maximum volumetric H2 production rates of MEC using Ni/Ti and Ni/GF cathodes were obtained at 0.39 ± 0.01 and 0.33 ± 0.03 m3 H2 m−3 d−1 respectively. The Ni/Ti and Ni/GF cathodes could be used as alternative cathodes while producing hydrogen from FE. [ABSTRACT FROM AUTHOR]

Palm oil mill effluent (POME) is a highly polluted agro-industrial wastewater. The CO2 in industrial flue gas requires treatment before it can be discharged into the environment. Utilizing microalgae as the agent to treat wastewater and industrial flue gas is a waste-to-wealth approach. The resulting biomass can be commercialized in the form of valuable products. Chlorella sp. is a microalgal species that can tolerate the pollutant load and has been proven to be a suitable species for CO2 fixation. In this study, Chlorella sp. was cultivated in POME with the aim of reducing the pollutants in the POME and simultaneously capturing CO2. The optimization of the operational conditions of this microalgae-based treatment system was carried out using the response surface methodology (RSM) face centered-central composite design (FC-CCD). Operational factors include the air concentration of CO2 (10-25% v/v), the inlet gas flow rate of 500-2000 mL min−1, and initial inoculum concentration (10-30% v/v) of Chlorella sp. cultivated in POME. The target deliverables include the maximum amount of CO2 fixed by Chlorella sp. and the total nitrogen (TN) reduction as indicators of pollutant reduction by this treatment system. We found that a limited supply of CO2 caused growth limitation, while excess CO2 resulted in acid production that triggered microalgae growth inhibition. The optimum operational conditions were 10% v/v CO2, 1670 mL min−1 aeration rate, and 24.8% v/v inoculum concentration, predicted to simultaneously fix CO2 at 0.12 g of CO2 L−1 day−1 and reduce 80.9% TN, respectively. [ABSTRACT FROM AUTHOR]

The dissolved CO 2 that causes ocean acidification has great potential for bioenergy production. In this study, we demonstrate that activated methanogens in waste sewage sludge (WSS) are useful for converting bicarbonate in seawater into methane. These activated methanogens were adapted in different seawater sources for methane production through repeated batch experiments that resulted in an increase of 300–400 fold in the methane yield. During these repeated batch experiments, the microbial communities in WSS adapted to the high salinity of seawater to generate more methane. Microbial community analysis showed the dominance of Achromobacter xylosoxidans, Serrati sp. and methanogens including Methanobacterium sp., Methanosarcina sp., and Methanosaeta concillii . Using a 13 C-labeled isotope, we demonstrate that 81% of the methane is derived from microbial conversion of NaH 13 CO 2 in artificial seawater. Therefore, this study shows that oceans, with the largest surface area on Earth, have a potential as a substrate for methane energy production via an acclimated consortium approach. [ABSTRACT FROM AUTHOR]

The management of waste activated sludge (WAS) recycling is a concern that affects the development of the future low-carbon society, particularly sludge reduction and biomass utilization. In this study, we investigated the effect of removing extracellular polymeric substances (EPS), which play important roles in the adhesion and flocculation of WAS, on increased sludge disintegration, thereby enhancing sludge reduction and methane production by anaerobic digestion. EPS removal from WAS by ethylenediaminetetraacetic acid (EDTA) significantly enhanced sludge reduction, i.e., 49 ± 5% compared with 27 ± 1% of the control at the end the digestion process. Methane production was also improved in WAS without EPS by 8881 ± 109 CH 4 μmol g −1 dry-weight of sludge. Microbial activity was determined by denaturing gradient gel electrophoresis and real-time polymerase chain reaction, which showed that the hydrolysis and acetogenesis stages were enhanced by pretreatment with 2% EDTA, with a larger methanogenic community and better methane production. [ABSTRACT FROM AUTHOR]

The stimulant and toxicity effects of reported organic (acetic acid, propionic acid, butyric acid, formic acid, oil & grease) and inorganic (copper) by-products presented in palm oil mill effluent on anaerobic bacterial population were examined in this paper. The toxicity test had shown that acetic, propionic and butyric acids tend to stimulate the bacterial density level (survival rate more than 50%), while formic acid, copper, oil and grease were shown to have suppressed the density level (survival rate less than 50%). The highest biomass recorded was 1.66 mg/L for the concentration of acetic acid at 216 mg/L and lowest biomass concentration, 0.90 mg/L for copper at 1.40 mg/L. Biohydrogen-producing bacteria have a favourable growth rate around pH 5.5. The comparison of half maximal effective concentration (EC 50) values between two test duration on the effects of organic and inorganic by-products postulate that bacteria had a higher tolerance towards volatile fatty acids. While acetic, butyric and propionic acids had exhibited higher tolerance EC 50 values for bacteria, but the opposite trend was observed for formic acid, copper and oil & grease. Image 1 • Acetic, butyric and propionic acid were proven to elevate bacterial biomass concentration. • Formic acid, copper, oil and grease have the ability to arrest bacterial growth. • Optimum pH for mixed culture anaerobic bacteria growth was mildly acidic. [ABSTRACT FROM AUTHOR]

Culture scaffolds allow microalgae cultivation with minimum water requirement using the air-liquid interface approach. However, the stability of cellulose-based scaffolds in microalgae cultivation remains questionable. In this study, the stability of regenerated cellulose culture scaffolds was enhanced by adjusting TiO 2 loading and casting gap. The membrane scaffolds were synthesized using cellulose dissolved in NaOH/urea aqueous solution with various loading of TiO 2 nanoparticles. The TiO 2 nanoparticles were embedded into the porous membrane scaffolds as proven by Fourier transform infrared spectra, scanning electron microscopic images, and energy-dispersive X-ray spectra. Although surface hydrophilicity and porosity were enhanced by increasing TiO 2 and casting gap, the scaffold pore size was reduced. Cellulose membrane scaffold with 0.05 wt% of TiO 2 concentration and thickness of 100 μm attained the highest percentage of Navicula incerta growth rate, up to 37.4%. The membrane scaffolds remained stable in terms of weight, porosity and pore size even they were immersed in acidic solution, hydrogen peroxide or autoclaved at 121 °C for 15 min. The optimal cellulose membrane scaffold is with TiO 2 loading of 0.5 wt% and thickness of 100 μm, resulting in supporting the highest N. incerta growth rate and and exhibits good membrane stability. [Display omitted] • The hydrophilicity of scaffolds enhanced with the increasing of TiO 2 nanoparticles. • The contact angle of scaffolds reduced to 38.5 ± 0.9° when 0.2 wt% TiO 2 added. • Scaffolds with 0.05 wt% TiO 2 and 100 μm showed the highest microalgae growth rate of 37.4%. • The membrane scaffolds remained stable even undergone sterilization. [ABSTRACT FROM AUTHOR]

Microalgae cultivation using open cultivation systems requires large area and it is susceptible to contamination as well as weather changes. Meanwhile, the closed systems require large capital investment, and they are susceptible to the build-up of dissolved oxygen. Air-liquid interface culture systems with low water-footprint, but high packing density can be used for microalgae cultivation if low-cost culture scaffolds are available. In this study, cellulose-based scaffolds were synthesized using NaOH/urea aqueous solution as the solvent. Titanium dioxide (TiO 2), silica gel and polyethylene glycol 1000 (PEG 1000) nanoparticles were added into the membrane scaffolds to increase the hydrophilicity of nutrient absorbing to support the growth of microalgae. The membrane scaffolds were characterized by FTIR, SEM, contact angle, porosity and porometry. All three nanoparticles additives showed their ability in reducing the contact angle of membrane scaffolds from 63.4 ± 2.3° to a range of 52.6 ± 1.2° to 38.8 ± 1.5° due to the hydrophilic properties of the nanoparticles. The decreasing in pore size when nanoparticles were added did not affect the porosity of membrane scaffolds. Cellulose membrane scaffold with TiO 2 showed the highest percentage of microalgae Navicula incerta growth rate of 22.1% because of the antibacterial properties of TiO 2 in lowering the risk of cell contamination and enhancing the growth of N. incerta. The results exhibited that cellulose-based scaffold with TiO 2 added could be an effective support in plant cell culture field. [Display omitted] • Cellulose-based scaffolds were synthesized using cellulose dispersed in NaOH/urea solvent. • Nanoparticles were added to enhance scaffold properties. • The contact angle of membrane scaffolds reduced to 38.8 ± 1.5° due to hydrophilicity. • Scaffold with TiO 2 nanoparticles showed the highest microalgae growth rate of 21.7%. • Nutrient adsorption of microalgae was enhanced by air-liquid interface cultivation. [ABSTRACT FROM AUTHOR]

Microalgae cultivation in open ponds requires a large footprint, while most photobioreactors need improvement in the ratio of surface to volume and energy consumption. In this study, polyethersulfone (PES) and poly(vinylidene fluoride) (PVDF) hollow fiber membranes with a large surface area were rearranged into open-ended and dead-ended configurations to improve the air-liquid interface cultivation of Navicula incerta. N. incerta were successfully grown on the porous membrane surface with the nutrients circulating inside the lumen. Fourier-transform infrared spectra showed the accumulation of polysaccharides, proteins and humic acids. Hydrophilic polysaccharides reduced water contact angles on PES and PVDF membranes to 37.2 ± 2.6° and 55.7 ± 3.3°, respectively. However, the porosity of PES (80.1 ± 1.1%) and PVDF (61.3 ± 4.5%) membranes were not significantly affected even after cultivation and harvesting of N. incerta. Scanning electron images further confirmed that N. incerta , cell debris and extracellular organic matter accumulated on the membrane. With large pores and a hydrophobic surface, PVDF hollow fiber membranes offered a greater improvement in N. incerta cell growth rate compared to PES hollow fiber membranes despite using different configurations. In the dead-ended configuration, they even attained the greatest improvement in N. incerta growth rate, up to 54.0%. However, PES hollow fiber membranes only achieved improvement in harvesting efficiency within the range of 18.7–38.0% due to weak cell adhesion. PVDF hollow fiber membranes significantly promoted the growth of microalgae N. incerta through the air-liquid interface system, leading to potential applications in wastewater treatment. [Display omitted] • PES and PVDF hollow fiber membranes were rearranged for the air-liquid interface cultivation. • Microalgae grew on the membrane surface with the nutrients circulating inside the lumen. • Membrane porosity remained after cultivation and harvesting through air purge. • PVDF membrane with large pores and a hydrophobic surface promoted cell growth rate. • The dead-ended configuration attained an improvement of 54.0% in cell growth rate. [ABSTRACT FROM AUTHOR]

Palm oil mill effluent (POME) contains nutrients such as carbon, nitrogen and phosphorus, and poses a threat to the environment especially if released untreated into water bodies. The phylum Chlorophyta contains microalgae from the genus Scenedesmus which are utilised as bioremediation agents. This study was conducted to evaluate the performance of Scenedesmus sp. UKM9 to remove chemical oxygen demand (COD) and nutrients (NH 4 + and PO 4 3−) from anaerobic POME by considering photoperiods and pollutant loading rates as environmental parameters. The results showed that the removal of COD (57% removal) and NH 4 + (100% removal) was the highest in a 12h:12h (light:dark) photoperiod and a pollutant loading rate of 61.67 mg L−1 day−1 COD. Removal of PO 4 3− (91% removal) was highest in a 16h:8h (light:dark) photoperiod and a pollutant loading rate of 11.67 mg L−1 day−1 COD. The removal of COD, nitrogen and phosphate occurred via the actions of microalgae through assimilation, bacteria through oxidation and precipitation through the formation of calcium phosphate complexes. These findings suggest that Scenedesmus sp. strain UKM9 is a potential bioremediation agent for treating POME. [Display omitted] • Cultivation of Scenedesmus sp. strain UKM9 in palm oil mill effluent (POME). • Effect of photoperiods and pollutant loading rates were investigated. • High removal of COD and NH 4 + in 12 h compared to 24 h photoperiod. • High removal of PO 4 3− 16 h photoperiod. • Scenedesmus sp. strain UKM9 is a potential bioremediation agent for treating POME. [ABSTRACT FROM AUTHOR]