Pretreatment Of Algal Biomass Research Articles

Innovations in algal biorefineries for production of sustainable value chain biochemicals from the photosynthetic cell factories

The concept of biorefinery can explore and expand new dimensions of bio-based commodity production, which will be crucial for sustainable economic growth. A biorefinery is likely to transform biomass into renewable energy and bioenergies for human wellbeing, such as pigments, proteins and biopolymers. Photosynthetic biomass (plant and algae-based), utilized atmospheric CO2 fixation and cheaper substrates (industrial byproducts) with simultaneous production of high value renewables (HVRs). However, due to their high potential of CO2 sequestration, utilization of wastewaters, algae could be considered a potential candidate as compared to terrestrial plants. In addition, pretreatment of algal biomass, its conversion and utilization are cheaper as compared to lignocellulosic waste. Techniques such as gasification, torrefaction, hydrothermal liquefaction can be utilized for the generation of bio-oil/biocrude, syngas, ash, and others, which can effectively be used for fuels and HVRs, respectively. Further, algal cultivation can also pose a potential advantage in terms of a zero-waste biorefinery as algal biomass consists of various proteins, lipids, carbohydrates, pigments and other bioactive components that can be utilized is different industrial sectors including cosmetics, nutraceuticals, and pharmaceuticals. However, alternative technology is required to reduce their production and extraction cost, where resources need to be utilized in a sustainable manner. In this context, the usage of some recyclable solvents such as green-solvents/ionic liquids to extract bioactive components without the cell disruption can acts as an effective technology for improving the algal biorefinery. Such “milking” technologies need further optimization of downstream processes to make it cost-effective. Similarly, for the upstream microalgal cultivation, biorefinery approach can combined with wastewater treatment/ bioremediation and GHG sequestration/ flue gas supplementation can be a promising approach to reduce the production cost. Therefore, with these advancements, an algal biorefinery can efficiently generate higher revenues. In this review, we discuss various upstream and downstream processing strategies and the potential possibilities, challenges and future perspectives of an algal biorefinery system has been discussed.

Microorganism‐Assisted Biohydrogen Production and Bioreactors

AbstractMicroorganism‐assisted biohydrogen (BioH2) is an encouraging replacement of fossil‐based fuels as feasible preference for various chemical and mechanical processes. BioH2 is capable to reduce greenhouse gas emissions and solve environmental issues, therefore, numerous studies addressed optimization of operation design, microbial actions, certain addition of chemicals or nanoparticles, pretreatment of algal biomass, diminishing sensibility of enzymes towards O2, integration with different processes for biorefinery approach, reducing costs, bioelectrochemical cell membranes, and others. The present review focuses on model organisms employed for the microorganism‐assisted biohydrogen production. Metabolic pathways such as biophotolysis, photofermentation, and dark fermentation were discussed for providing deep insight of microorganism‐aided biohydrogen production.

Enzymatic pretreatment of algal biomass has different optimal conditions for biogas and bioethanol routes

Enzymatic pretreatment is emerging as an efficient tool for the extraction of biofuel precursors from algal biomass. However, yardsticks for end-use directed selection of optimal pretreatment conditions are not yet identified. The present study, for the first time, reveals different optimal conditions for algal biomass solubilization and sugar release. Algal biomass pretreatment optimization was carried out using the Taguchi method. Crude enzyme from Aspergillus fischeri was found effective for pretreatment of Chlorella pyrenoidosa. Maximum sugar yield (190 mg g−1 biomass) from algal biomass was observed at a substrate concentration of 4 g L-1, with a 5% enzyme load at temperature 60°C, pH 5.5, and shaking speed of 80 rpm. In contrast, maximum sCOD (1350 mg g−1 biomass) was obtained at 2 g L−1 substrate concentration with enzyme load of 20% v/v, at 60°C, pH 4, and shaking speed of 100 rpm. Hence, the first set of conditions would be more beneficial for bioethanol production. Whereas another set of conditions would improve the biofuel production that requires maximum solubilization of algal biomass, such as fermentative methane production. Overall, the present observations established that process conditions required for enzymatic pretreatment of algal biomass should be selected according to the desired biofuel type.

Current prospects and future developments in algal bio-hydrogen production: a review

The use of fossil fuels for energy demands is insufficient for escalating demands as they are limited in nature and are not environment friendly. Various microbial sources are under scanner for clean energy production out of which algae comes as a promising one. Production of biohydrogen from algae has brought a lot of hopes in the energy production sector. Algae are powerhouse of renewable chemicals including biofuel precursors. Biohydrogen is one of such biofuel precursors; it proves to be a clean and sustainable fuel and can be produced in industries. Currently however, it cannot stand up to the present energy demands of the world due to certain obstacles, such as cost effectiveness, storage and transportation of hydrogen. One of the main hurdles in algal biofuel technology is the rigid nature of algal cell wall. To get around this, pretreatment of algal biomass is imperative to overcome productivity issues, so as not to compromise biofuel yield. Improving the biofuel production at every step can make a huge difference in outcomes and thus comes up as a promising tool. Therefore, in the present state of art review, various methods of algal biomass pretreatment, different enzymes involved in hydrogen production, various factors influencing hydrogen production from algae and genetic engineering avenues have been discussed in brief.

Phycoremediation of wastewater by Chlorella pyrenoidosa and utilization of its biomass for biogas production

This study aims to focus on simultaneous wastewater treatment and clean energy production using Chlorella pyrenoidosa (C. Pyrenoidosa) microalgae. The growth of C. Pyrenoidosa is performed in real sewage treatment plant wastewater (STPW) and synthetic wastewater (SWW). During its growth the C. Pyrenoidosa, reduces the nitrate, phosphate and chemical oxygen demand (COD) as 99.2%, 70.1%, and 61.0%, respectively from SWW; for STPW these values are 99.5%, 94.2%, and 87.1%, respectively. The growth of C. Pyrenoidosa is studied in terms of algal biomass generation and used for biogas production by anaerobic digestion in the presence of anaerobic microorganisms. The pretreatment methods such as thermal (temperature 900 °C, time 8 h), hydrothermal (temperature 121 °C, pressure 15 psi, time 15 min), ultrasonic (power 100 W, time 15 min) and Fenton (speed 140 rpm, time 3 h) are used for pretreatment of algal biomass to enhance the biogas production. Total biogas yield of 479 mL and methane yield of 147 mL/volatile solid (g) are obtained from untreated algal biomass. Ultrasonic, thermal, hydrothermal and Fenton pretreated microalgae biomass show 15.5%, 8.2%, 18.4% and 10.9% enhancement in methane production, respectively; while for total biogas production, the corresponding values are 7.93%, 10.43%, 14.19% and 11.06%, respectively.

Current trends and prospects in microalgae-based bioenergy production

Abstract Algae are fast-growing, microscopic, and eukaryotic organisms that can perform photosynthesis, and simultaneously fix atmospheric CO2. Algal cells contain high quantity of biofuel precursors such as starch and lipid granules. In the past decades, microalgal biomass has emerged as a potential feedstock for bioenergy generation. In the current scenario, it is being extensively explored to produce liquid (bioethanol, biodiesel) and gaseous (biomethane, biohydrogen) fuels. Algal technology has four crucial aspects including strain selection and its cultivation, harvesting techniques, conversion routes, and pretreatment of biomass. The quality and quantity of biomass, available media source, cultivation system as well as environmental conditions collectively help in the selection of the specific algal strain. Despite several in-depth attempts, there are various hurdles and limitations to make algal biofuel technically and economically viable. To meet the operational and economic feasibility, a collective approach is desirable. The present state-of-the-art review deals with all four crucial aspects of algal technology. The manuscript especially covers the significant methods of harvesting, energy conversion, and pretreatment. Moreover, it also revels the advantage of biological agent mediated harvesting, energy conversion and the pretreatment of algal biomass for sustainable biofuel recovery. The prime objective of this review is to give an insight into the aspects of algal technology to promote collective research in the area of algal biofuel.

A novel energetically efficient combinative microwave pretreatment for achieving profitable hydrogen production from marine macro algae (Ulva reticulate)

This study aims to enhance the hydrogen (H2) production from marine macro algae (Ulva Reticulate) by microwave combined with hydrogen peroxide (H2O2) under alkaline condition. Microwave (domestic type) (M) pretreatment of algal biomass at its optimal power (40%) resulted in 27.9% COD solubilization at 15 min time interval. When this optimal microwave power was combined with H2O2 (MH) an increment in COD solubilization was achieved at 24 mg H2O2/g macroalgae dosage. Under alkaline condition (pH 7–12), microwave and H2O2 combination (MHA) yielded better result than MH. At optimal alkaline condition (pH 10), MHA pretreatment shows a COD solubilization of 34%. Microwave in alkaline condition induces decomposition of H2O2 and more OH radical synthesis. This synergistically promotes solubilization. The MHA process considerably diminish time and specific energy required for biomass disintegration. Among the samples, highest H2 yield of 87.5 mL H2/g COD was observed for MHA.

Enzymatic pretreatment of algal biomass for enhanced conversion to biogas

"This paper presents a method for the enzymatic pretreatment of algal biomass used as a fermentation substrate in anaerobic bioreactors for biogas production, in order to improve the energy efficiency of the biogas systems. The pretreatment method aims at breaking compact carbohydrates (cellulose and hemicelluloses) macromolecular structures from algal biomass under the action of a hydrolytic enzymes mixture secreted by the fungal species Trichoderma reesei, Trichoderma versicolor, Penicillinum chrysosporium, Fusarium solani, Chaetomium thermophile and Myrothecium verrucaria, thus facilitating access of anaerobic fermentation bacteria to heavily biodegradable cellulosic fibres, reducing fermentation time length and implicitly increasing the biomethane yield of anaerobic reactors. The laboratory experiments involving the marine macroalgae Ulva sp. have proven a significant increase in the concentration and total volume of biomethane in the fermentation gas produced by the enzymatically pretreated sample with the selective fungal mixture, compared to the untreated sample. It is expected that such a non-corrosive pretreatment method can bring higher biomethane production with minimal conditioning costs and fewer process residues, thus increasing the biogas systems profitability."

Synergetic pretreatment of algal biomass through H2O2 induced microwave in acidic condition for biohydrogen production

The objective of the present study is to improve the biohydrogen production from marine macroalgae (Ulva reticulate) by acidic - hydrogen peroxide (H2O2) induced microwave (AHMW) pretreatment. Higher soluble chemical oxygen demand (SCOD) release of 1450 mg/L and its liquefaction rate of 30.2% was achieved in microwave (MW) pretreatment with treatment time period of 15 mins. Varying concentration of H2O2 from 0.003 to 0.03 g/g TS were used in the optimal microwave power (40%) to enhance the organic release in H2O2 induced microwave pretreatment (HMW). Maximum liquefaction of 33.9% was obtained at the H2O2 concentration of 0.024 g /g TS. The combined HMW pretreatment under acidic (pH 4–6.5) show synergistic effect on organic release. At optimal pH 5, AHMW pretreatment shows the SCOD release of 1850 mg/L with its liquefaction of 38.5% at time of 10 min. Therefore, AHMW pretreatment significantly reduce the treatment time and increase liquefaction when compared to MW and HMW. The maximum biohydrogen production was observed as 92.5 mL H2/g COD in AHMW pretreatment.

Conjoint effect of microwave irradiation and metal nanoparticles on biogas augmentation from anaerobic digestion of green algae

Pretreatment of biomass is a commonly applied technique for improving its biodegradability; however, such methods are energy intensive, which affects the overall efficiency. This study aims to provide an energy efficient solution by combining microwave (MW) pretreatment of algal biomass (Enteromorpha) and metal nanoparticles (NPs). The MW pretreatment of the biomass was in the form of a slurry (liquid:solid 20:1), while pretreatment time and MW pretreatment power were 6min and 600 W, respectively. Nickel (Ni) and Cobalt (Co) NPs with a concentration of 1 mg/L were used. Batch-wise anaerobic digestion was carried out for a period of 264 h. The results showed that MW pretreatment initiates early hydrolysis of green algae thus reducing lag time. NPs had a positive influence in biogas production at the later stages of anaerobic digestion. The highest total biogas production of 53.60ml/gTS was attained by Co NPs + MW pretreatment whereas maximum biohydrogen of 59.52% (v/v) was produced by Ni NPs + MW pretreatment group. Energy analysis showed that combined utilization of MW pretreatment and metal NPs produced added energy while consuming less input energy than MW pretreatment alone. The kinetic parameters were calculated by using modified Gompertz and Logistic function model for each experimental case.

Microalgae cultivation for wastewater treatment and biogas production at Moscow wastewater treatment plant.

The process of cultivation of microalgae on purified and clarified wastewater of Kuryanovo wastewater treatment plants (KWWTP) was studied. The studies were conducted on monoculture (Scenedesmus quadricauda and Chlorella sorokiniana) and on polyculture, the composition of which was formed from microalgae present in the wastewater. The authors created and investigated the columnar photobioreactor (PBR), which acted as a pilot project on the purified and clarified water of KWWTP and allowed the removal of total nitrogen and phosphorus phosphates with an efficiency of up to 90%. The formation of a stable biocenosis from 22 species of algae (with 3-4 dominant species) and 31 species of zooplankton organisms belonging to six systematic subdivisions was recorded. The optimal retention time of the microalgae polyculture for the most effective wastewater treatment has been determined. The conducted studies have shown that the depth of decomposition of ashless matter and the ultimate biogas potential of untreated microalgae biomass is 15% lower than the corresponding values obtained with digestion of activated sludge, which necessitates studies in the field of pretreatment of algal biomass. The paper shows: connections between chlorophyll-a content, algal biomass and fluorescence index F0 and between biomass increment and Fv/Fm value.

A method for simultaneous bioflocculation and pretreatment of algal biomass targeting improved methane production

A novel fungi mediated method for simultaneous bioflocculation and pretreatment of algae, to improve the methane yield, is revealed.

Hydroxyl radical-aided thermal pretreatment of algal biomass for enhanced biodegradability.

BackgroundAlgal biomass, known as a potential feedstock for biofuel production, has cell wall structures that differ from terrestrial biomass. The existing methods for processing algae are limited to conventional pretreatments for terrestrial biomass. ResultsIn this study, we investigated a novel hydroxyl radical-aided approach for pretreating different types of algal biomass. In this process, hydroxyl radicals formed by a Fenton system were employed in combination with heating to alter the crystalline structure and hydrogen bonds of cellulose in the algal biomass. FeSO4 and H2O2 at low concentrations were employed to initiate the formation of hydroxyl radicals. This method releases trapped polysaccharides in algal cell walls and converts them into fermentable sugars. The effects of temperature, time, and hydroxyl radical concentration were analyzed. The optimal pretreatment condition [100 °C, 30 min, and 5.3 mM H2O2 (determined FeSO4 concentration of 11.9 mM)] was identified using a central composite design. Complete (100 %) carbohydrate recovery was achieved with some algal biomass without formation of inhibitors such as hydroxymethylfurfural and furfural as by-products. Both microalgal and macroalgal biomasses showed higher enzymatic digestibility of cellulose conversion (>80 %) after the milder pretreatment condition.ConclusionHydroxyl radical-aided thermal pretreatment was used as a novel method to convert the carbohydrates in the algal cell wall into simple sugars. Overall, this method increased the amount of glucose released from the algal biomass. Overall, enhanced algal biomass digestibility was demonstrated with the proposed pretreatment process. The new pretreatment requires low concentration of chemical solvents and milder temperature conditions, which can prevent the toxic and corrosive effects that typically result from conventional pretreatments. Our data showed that the advantages of the new pretreatment include higher carbohydrate recovery, no inhibitor production, and lower energy consumption. The new pretreatment development mimicking natural system could be useful for biochemical conversion of algal biomass to fuels and chemicals.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0372-2) contains supplementary material, which is available to authorized users.

Pretreatment of algal biomass using fungal crude enzymes

In the present study, two fungal strains were tested for production of crude enzyme using sugarcane bagasse. The fungal crude enzymes were tested for algal biomass pretreatment. The visual observations along with the microscopic (phase contrast and scanning electron microscopy) analysis and automated cell counter imaging modes involving sytox green staining confirmed the efficient action of fungal crude enzyme on algal cells. Furthermore, upon quantitative analysis, it was observed that 20% dose (v/v) of Aspergillus lentulus crude enzyme (AL2) had a significant pretreatment effect on Chroococcus sp. biomass. AL2 resulted in nearly 100% cell death of Chroococcus sp. within 48h incubation at 30°C. Additionally, up to 44% and 46% of total sugar and COD of biomass, respectively, were also solubilised with the action of AL2. As the investigated method showed good capabilities in solubilising the algal biomass, it holds great application potential for algal biofuel production where algal biomass pretreatment is required. However, further attempts are needed to optimize the process parameters of investigated pre-treatment process in order to make it feasible and widely acceptable.

Enhanced methane production from algal biomass through short duration enzymatic pretreatment and codigestion with carbon rich waste

Novel two fold approach comprising short duration fungal crude enzyme pretreatment of algal biomass followed by codigestion with cattle dung resulting in enhanced methane yield is disclosed.

Comparative Effects of Biomass Pre-Treatments for Direct and Indirect Transesterification to Enhance Microalgal Lipid Recovery

Microalgal lipid recovery for biodiesel production is currently considered suboptimal, but pre-treatment of algal biomass, the use of solvent mixtures and the positioning of transesterification can lead to increased yields. Here, the effect of various reportedly successful pre-treatments and solvent mixtures were directly compared to each other and combined with direct and indirect transesterification methods using the oleaginous microalga Tetraselmis sp. M8. Microwave and thermal pre-treatments were applied and the total lipid and fatty acid methyl ester (FAME) recoveries were investigated. The application of pre-treatments increased FAME recovery through indirect transesterification when a Soxhlet system was used but they had no significant effect for direct transesterification. Gravimetric analyses of total lipids revealed that lipid recovery was highest when utilizing the chloroform-based Bligh and Dyer extraction method; however FAME yield was the highest when applying a Soxhlet system utilizing a solvent mixture of hexane-ethanol (3:1). Total lipid recovery did not necessarily correlate with the recovery of FAMEs. The highest FAME recovery was achieved from thermal or microwave pre-treated biomass followed by indirect transesterification through Soxhlet extraction. FAME recovery could be more than doubled (increase of up to 171%) under these conditions. We conclude that a simple thermal pre-treatment (80°C for 10 min) in combination with solvent mixture extraction through indirect transesterification may present a cost-effective and scalable option for large-scale lipid extraction from microalgae.