This study describes the method development for bioethanol production from three species of seaweed. Laminaria digitata, Ulva lactuca and for the first time Dilsea carnosa were used as representatives of brown, green and red species of seaweed, respectively. Acid thermo-chemical and entirely aqueous (water) based pre-treatments were evaluated, using a range of sulphuric acid concentrations (0.125–2.5 M) and solids loading contents (5–25 % [w/v]; biomass: reactant) and different reaction times (5–30 min), with the aim of maximising the release of glucose following enzyme hydrolysis. A pre-treatment step for each of the three seaweeds was required and pre-treatment conditions were found to be specific to each seaweed species. Dilsea carnosa and U. lactuca were more suited with an aqueous (water-based) pre-treatment (yielding 125.0 and 360.0 mg of glucose/g of pretreated seaweed, respectively), yet interestingly non pre-treated D. carnosa yielded 106.4 g g−1 glucose. Laminaria digitata required a dilute acid thermo-chemical pre-treatment in order to liberate maximal glucose yields (218.9 mg glucose/g pre-treated seaweed). Fermentations with S. cerevisiae NCYC2592 of the generated hydrolysates gave ethanol yields of 5.4 g L−1, 7.8 g L−1 and 3.2 g L−1 from D. carnosa, U. lactuca and L. digitata, respectively. This study highlighted that entirely aqueous based pretreatments are effective for seaweed biomass, yet bioethanol production alone may not make such bio-processes economically viable at large scale.
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Brown seaweeds lack lignin and have a low cellulose content. Thus, seaweeds should be an easier material for biological degradation than land plants. However, seaweeds have a complex composition, and complete degradation of the material necessitates the presence of microorganisms with a broad substrate range. During anaerobic degradation of organic material, energy carriers such as methane and ethanol may be produced. This is a study of two particular species of brown seaweeds; Laminaria hyperborea and Ascophyllum nodosum, which are the most abundant Norwegian species and also the two species that are commercially harvested in Norway.
Most of the degradation studies were carried out in batch systems at pH 7 and at 35 °C. The digestion pattern of the seaweeds were studied by measuring gas production, alginate lyase activity, remaining alginate, the concentrations of uronic acids, VS, COD, mannitol, organic acids and polyphenols. NIR spectroscopy was applied as a new method for alginate quantification. Ethanol production was carried out at 30 °C at different pH, both in batch and continuous cultures. Gas production and concentrations of mannitol, laminaran, ethanol and organic acids were measured.
Methane is the end product of a mixed microbial community. However, it is the initial steps of hydrolysis and acidogenesis that are specific for the raw material. Alginate forms the major structural component of brown algae, and its degradation is catalysed by alginate lyases. Polyphenols proved to be the most important limiting factor in the biodegradation: the content of polyphenols was much higher in A. nodosum than L. hyperborea, and this led to a reduced biodegradability of A. nodosum. However, when the polyphenols were fixed with formaldehyde, this seaweed was also readily degraded. Manipulation of the content of polyphenols in L. hyperborea gave similar results. This toxic effect was probably caused by direct inhibition of the microbes, especially the methanogenic bacteria, and complexation reactions with algal material and enzymes. Generally, the guluronate content of the remaining alginate increased during biodegradation, probably due to the Ca-linked guluronate junction zones less accessible for alginate lyase. The main organic product of the acidogenesis was acetate, which was easily converted to methane. In this study, it was not attempted to optimise the methane yield.
Ethanol is an intermediate in the complete digestion of organic material and is produced by specific microbial strains. Thus, ethanol production should take place under controlled conditions to prevent contamination problems. The complex composition of seaweeds makes it a difficult substrate to ferment to ethanol by one or a few strains of microbes. In this work, laminaran and mannitol extracted from L hyperborea fronds were used as substrate for ethanol production. A bacterium, Zymobacter palmae, was able to produce ethanol from mannitol, but could not utilise laminaran. However, the yeast Pichia angophorae was able to produce ethanol from both substrates simultaneously. Some supply of oxygen was necessary for the fermentation of mannitol, while a too high aeration resulted in the production of organic acids.
Thus, it has been shown that both methane and ethanol can be produced from brown seaweeds. However, an optimisation of the processes will be necessary. Energy production from seaweeds will only be economic if the harvesting costs are low. It may be noted that wastes from the alginate industry may be considered a non-cost raw material for energy production.
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The Green Revolution boosted agricultural production approximately 2.5 times and was associated with an approximately 40% price reduction in the cost of food (MA, 2005). Following on the euphoria of this success there has been increasing pressure to diversify production and to improve the planet’s environment (Hubert et al., 2010). Successful realization of this pressure will require better soil management. However, current conditions are very different from what they were 50 years ago. The success of the Green Revolution came at the expense of the natural capital, such that 18 of the 24 currently acknowledged ecosystem services have been impaired. Although soils have aided climate regulation by sequestering an estimated 2 Gt carbon (C) per annum from fossil fuel burning, they have lost part of their capacity to regulate hydrological fluxes and nutrient cycles and therefore to support plant production. The soils of the earth are now being asked to produce 70% more food over the next 35 years, while also producing biofuels, regulating climate through further C sequestration, and helping to conserve biodiversity. However, the other side of this coin is the declining amount of land remaining available for conversion to agroecosystems and the increased cost of energy, which has led to a substantial increase in the price of fertilizers. Further, world sources of phosphorus (P) are being rapidly depleted and the toxic effects of pesticides are now forcing the replacement of these former pillars of intensive agriculture with new technical options. Agriculture now needs to sustain high levels of production while preserving or restoring the natural capital of the soil. Maintenance of an appropriate level of soil biodiversity is critical to achieving this goal, but in order to protect the soil resource and optimize its long-term use, new land use practices are needed to be developed, based on much greater understanding of the factors controlling its functioning. This article summarizes the current knowledge of the composition and taxonomic richness of the soil biota. It then examines the participation of the soil biota in the major soil functions and discusses ways to reconcile the conservation and/or improvement of this natural capital with the production of critical ecosystem goods and services.
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Through the years, several strains and color morphotypes of Kappaphycus and Eucheuma have emerged in cultivation areas as a result of environmental and anthropogenic factors. This led to confusion in nomenclature of these seaweeds. However, the advent of molecular technology has brought notable changes to seaweed research over the past two decades. New molecular techniques have proved useful, particularly in the molecular identification and cataloging of economically important carrageenophytes, i.e. Kappaphycus and
Eucheuma which were commercially introduced into many countries worldwide. The following chapter discusses the application and findings of molecular studies within the context of these red seaweeds, along with potential areas for future research.
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Energy security, high atmospheric greenhouse gas levels, and issues associated with fossil fuel extraction are among the incentives for developing alternative and renewable energy resources. Biofuels, produced from a wide range of feedstocks, have the potential to reduce greenhouse gas emissions. In particular, the use of microalgae as a feedstock has received a high level of interest in recent years.
Microalgal biofuels are promising replacement for fossil fuels and have the potential to displace petroleum-based fuels while decrease greenhouse gas emissions. The primary focus of research and development toward algal biofuels has been on the production of biodiesel or renewable diesel from the lipid fraction, with use of the non-lipid biomass fraction for production of biogas, electricity, animal feed, or fertilizer.
Since the non-lipid fraction, consisting of mainly carbohydrates and proteins, comprises approximately half of the algal biomass, our approach is biological conversion of the lipid-extracted algal biomass (LEAB) into fuels. We used LEAB from Nannochloropsis salina, and ethanol was the model product. The first step in conversion of LEAB to ethanol was deconstruction of the cell wall into fermentable substrates by using different acids or enzymes. Sugar release yields and rates were compared for different treatments. One-step sulfuric acid hydrolysis had the highest yield of released sugars, while the one-step hydrochloric acid treatment had the highest sugar release rate. Enzymatic hydrolysis produced acceptable sugar release rates and yields but enzymes designed for algal biomass deconstruction are still needed. Proteins were deconstructed using a commercially available protease.
The hydrolysate, containing the released sugars, peptides, and amino acids, was used as a fermentation medium with no added nutrients. Three ethanologenic microorganisms were used for fermentation: two strains of Saccharomyces cerevisiae (JAY270 and ATCC 26603) and Zymomonas mobilis ATCC 10988. Ethanol yields and productivities were compared. Among the studied microorganisms, JAY270 had the highest ethanol yield while Z. mobilis had the lowest yield for most of the studied conditions. A protease treatment improved the biomass and ethanol yields of JAY270 by providing more carbon and nitrogen.
To increase ethanol productivity, a continuous fermentation approach was adapted. Continuous stirred tank reactors have increased productivity over batch systems due to lower idle time. The downtime associated with batch fermentation is the time it takes for empting, cleaning, and filling the reactor. Productivity in the continuous fermentation was limited by the growth characteristics of the microorganism since at high flow rates, with washout occurring below a critical residence time. To overcome the washout problem, the use of an immobilized cell reactor was explored. The performance (ethanol productivity) of free and immobilized cells was compared using an enzymatic hydrolysate of LEAB. Higher ethanol productivities were observed for the continuous immobilized cell reactor compared to the stirred tank reactor.
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A PDF Power Point slide on "Bioconversion of Biofuel Resides into Aquatic Feed".
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The present investigation was targeted on anaerobic digestion of Chroococcus sp. and utilization of resul- tant ‘‘Liquid Digestate’’ for its further biomass production. The algal biomass has biomethane potential of 317.31 ± 1.9 mL CH4 g1 VSfed. Regular process monitoring revealed that process was stable throughout the experiments. The ‘‘Liquid Digestate’’ was explored as nutrient supplement for further algal growth. Diluted ‘‘Liquid Digestate’’ (30% concentration) was found optimal for algal growth (0.79 ± 0.064 g L1). Simultaneously, 69.99–89.31% removal in nutrient and sCOD was also recorded with algal growth. Inter- estingly, higher growth was observed when rural sector wastewater (1.29 ± 0.067 g L1) and BG11 broth (1.42 ± 0.102 g L1) was used for diluting the ‘‘Liquid Digestate’’. The current findings have practically proven the feasibility of hypothesized ‘‘closed loop process’’.
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The recent and unexpected finding that methanogenic bacteria occupy an isolated biochemical island in the sea of procaryotes has added a touch of excitement to the study of these organisms1. This island is defined by such diverse biochemical qualities as: a very restricted range of oxidizable substrates coupled to the biosynthesis of methane; synthesis of an unusual range of cell-wall components; synthesis of biphytanyl glycerol ethers as well as high amounts of squalene; synthesis of unusual coenzymes and growth factors; synthesis of rRNA that is distantly related to that of typical bacteria; possession of a genome size (DNA) approaching 1/3 that of E. coli.
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The present paper deals with some important biochemical components such at proteins, carbohydrates and lipids of 33 marina algae, growing abundantly on the coast of Ramanathapuram District. The results indicated that the green algae (Chlorophyceae) has the maximum of protein content ranging from 6 to 25.8%, next in order comes the brown algae (Phaeophyceae) with13 to 16.6% followed by red algae (Rhodophyceae) with 1.5 to 8.8%. The range of carbohydrate content was from 0.3 to 11.6% in green algae, 3.3 to 24.9% in brown algae and 1.8 to 57.0% in red algae. The lipid content ranged from 0.6 to 8.6% in green algae, 0.6 to 3.7% in brown algae and 0.4 to 6.1% in red algae. The results of the study give an Insight into the biochemical content of the algal species studied could be used to decide their suitability for the formulation of feed to fishes in aquaculture and to other animals.
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Studies were made on protein, carbohydrate and lipid from 28 marine algae from Lakshadweep Islands. The protein content ranged from 0.1 to 18.9% in green algae, 4.6 to 12.2% brown algae and 2.7 to 13.1% in red algae. The carbohydrate content was from 0.5 to 15.846, 1.5 to 13.0% and 2.0 to 29.4% in gMn, brown and red algae respectively. The lipid content varied from 2.6 to 13.8% in green algae, 2.2 to 8.3% in brown algae and 3.1 to 8.3% in red algae
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