Optimization of saccharification and ethanol production by simultaneous saccharification and fermentation (SSF) from seaweed, Saccharina japonica

Direct Itaconate Production from Brown Macroalgae Using Engineered Vibrio sp. dhg

Itaconate is a promising platform chemical with broad applicability, including the synthesis of poly(methyl methacrylate). Most studies on microbial itaconate production entail the use of crop-based feedstock, which imposes constraints due to its limited supply. Brown macroalgae have recently gained attention as next-generation biomass owing to their high biomass productivity and carbohydrate content and amenability to mass production. Therefore, the use of macroalgae for itaconate production warrants exploration. In this study, the direct production of itaconate from brown macroalgae was demonstrated using engineered Vibrio sp. dhg, which has emerged as an efficient platform host for brown macroalgal biorefineries. Specifically, to enhance production, cis-aconitate decarboxylase (Cad) from Aspergillus terreus was heterologously expressed and isocitrate dehydrogenase (icd) was deleted. Notably, the resulting strain, VIC, achieved itaconate titers of 2.5 and 1.5 g/L from a mixture of alginate and mannitol (10 g/L of each) and 40 g/L of raw Saccharina japonica (S. japonica), respectively. Overall, this study highlights the utility of brown macroalgae as feedstock, as well as that of Vibrio sp. dhg as a platform strain for improving itaconate bioproduction.

Exploring the Prospects of Fermenting/Co-Fermenting Marine Biomass for Enhanced Bioethanol Production

With the rising demands for renewable fuels, there is growing interest in utilizing abundant and sustainable non-edible biomass as a feedstock for bioethanol production. Macroalgal biomass contains a high content of carbohydrates in the form of special polysaccharides like alginate, agar, and carrageenan that can be converted to fermentable sugars. In addition, using seagrass as a feedstock for bioethanol production can provide a sustainable and renewable energy source while addressing environmental concerns. It is a resource-rich plant that offers several advantages for bioethanol production, including its high cellulose content, rapid growth rates, and abundance in coastal regions. To reduce sugar content and support efficient microbial fermentation, co-fermentation of macroalgae with seagrass (marine biomass) can provide complementary sugars and nutrients to improve process yields and economics. This review comprehensively covers the current status and future potential of fermenting macroalgal biomass and seagrass, as well as possible combinations for maximizing bioethanol production from non-edible energy crops. An overview is provided on the biochemical composition of macroalgae and seagrass, pretreatment methods, hydrolysis, and fermentation processes. Key technical challenges and strategies to achieve balanced co-substrate fermentation are discussed. The feasibility of consolidated bioprocessing to directly convert mixed feedstocks to ethanol is also evaluated. Based on current research, macroalgae-seagrass co-fermentation shows good potential to improve the bioethanol yields, lower the cost, and enable more optimal utilization of diverse marine biomass resources compared to individual substrates.

Brown algae and their multiple applications as functional ingredient in food production

Brown algae are considered one of the resources that can contribute to transforming our global food system by promoting healthier diets and reducing environmental impact. In this sense, this review article aims to provide up-to-date information on the nutritional and functional improvement of brown algae when they are applied to different food matrices. Brown algae present sulfated polysaccharides (alginates, fucoidans, and laminarins), proteins, minerals, vitamins, dietary fibers, fatty acids, pigments, and bioactive compounds that can positively contribute to the development of highly nutritious food products, as well as used reformulate products already existing, to remove, reduce, increase, add and/or replace different components and obtain products that confer health-promoting properties. This review demonstrates that there is a tendency to use seaweed for the production of functional foods and that the number of commercially produced products from seaweed is increasing, that is, seaweed is a sector whose global market is expanding.

Metabolic engineering for valorization of macroalgae biomass

Marine macroalgae have huge potential as feedstocks for production of a wide spectrum of chemicals used in biofuels, biomaterials, and bioactive compounds. Harnessing macroalgae in these ways could promote wellbeing for people while mitigating climate change and environmental destruction linked to use of fossil fuels. Microorganisms play pivotal roles in converting macroalgae into valuable products, and metabolic engineering technologies have been developed to extend their native capabilities. This review showcases current achievements in engineering the metabolisms of various microbial chassis to convert red, green, and brown macroalgae into bioproducts. Unique features of macroalgae, such as seasonal variation in carbohydrate content and salinity, provide the next challenges to advancing macroalgae-based biorefineries. Three emerging engineering strategies are discussed here: (1) designing dynamic control of metabolic pathways, (2) engineering strains of halophilic (salt-tolerant) microbes, and (3) developing microbial consortia for conversion. This review illuminates opportunities for future research communities by elucidating current approaches to engineering microbes so they can become cell factories for the utilization of macroalgae feedstocks.

An overview and assessment of the existing technological options for management and resource recovery from beach wrack and dredged sediments: An environmental and economic perspective

The present work discusses the problems and management options of beach wrack and dredged sediments. Beach wrack and dredged sediments near the shores have affected the coastal ecosystem, badly. The piles of beach wrack residues might be a significant emitter of greenhouse gases (GHGs) and dredged sediment is a substantial source of heavy metals and other pollutants. The recovery of valuable resources such as metals and nutrients from these so-called "wastes" is a sustainable strategy to enhance the resilience of the coastal ecosystem and management. The beach wrack meadows can be a potential source for green energy production. Even the demand for biodegradable polymers can be supplied by utilizing the waste beach wracks. The residues of beach wrack species like Posidonia oceanica, Zostera marina, Ulva spc. and Enhalus acorodies can be very beneficial species in terms of economic growth. Red algae have been the most favored and efficient candidate for methane yield. In case of dredged sediment, dewatering of sediment is an essential step for successful resource extraction. Although, extraction methods are almost similar to that applied for soil treatment, which includes pretreatment, physical partitioning, washing, thermal treatment, biological extraction, and immobilization. The fractionation study can be a beneficial tool for determining the metal species present in the sediment. Immobilization techniques are successful but continuous monitoring is required. The vitrification technique is highly effective but very expensive. Thermal treatment is useful for volatile metals such as mercury (Hg), but costs are high. Biological extractions are comparatively cheap but time-consuming. Henceforth, very few extraction methods are available for sediment and required further advancement in this field.

Unraveling the unique butyrate re-assimilation mechanism of Clostridium sp. strain WK and the application of butanol production from red seaweed Gelidium amansii through a distinct acidolytic pretreatment

Exploration of the algae-derived biobutanol synthesis has become one of the hotspots due to its highly cost-effective and environment-friendly features. In this study, a solventogenic strain Clostridium sp. strain WK produced 13.96 g/L butanol with a maximal yield of 0.41 g/g from glucose in the presence of 24 g/L butyrate. Transcriptional analysis indicated that the acid re-assimilation of this strain was predominantly regulated by genes buk-ptb rather than ctfAB, explaining its special phenotypes including high butyrate tolerance and the pH-independent fermentation. In addition, a butyric acid-mediated hydrolytic system was established for the first time to release a maximal yield of 0.35 g/g reducing sugars from the red algal biomass (Gelidium amansii). Moreover, 4.48 g/L of butanol was finally achieved with a significant enhancement by 29.9 folds. This work reveals an unconventional metabolic pathway for butanol synthesis in strain WK, and demonstrates the feasibility to develop renewable biofuels from marine resources.

Biofuel production from Macroalgae: present scenario and future scope

The current fossil fuel reserves are not sufficient to meet the increasing demand and very soon will become exhausted. Pollution, global warming, and inflated oil prices have led the quest for renewable energy sources. Macroalgae (green, brown, and red marine seaweed) is gaining popularity as a viable and promising renewable source for biofuels production. Numerous researches have been conducted to access the potential of macroalgae for generating diverse bioproducts such as biofuels. The existence of components such as carbohydrates and lipids, and the lack or deficiency of lignin, create macroalgae an enviable feedstock for biofuels generation. This review briefly covers the potential macroalgal species promoting the production of biofuels and their cultivation methods. It also illustrates the biofuel generation pathway and its efficiency along with the recent techniques to accelerate the product yield. In addition, the current analysis focuses on a cost-effective sustainable generation of biofuel along with commercialization and scaleup.

Adaptive laboratory evolution principles and applications in industrial biotechnology

Adaptive laboratory evolution (ALE) is an innovative approach for the generation of evolved microbial strains with desired characteristics, by implementing the rules of natural selection as presented in the Darwinian Theory, on the laboratory bench. New as it might be, it has already been used by several researchers for the amelioration of a variety of characteristics of widely used microorganisms in biotechnology. ALE is used as a tool for the deeper understanding of the genetic and/or metabolic pathways of evolution. Another important field targeted by ALE is the manufacturing of products of (high) added value, such as ethanol, butanol and lipids. In the current review, we discuss the basic principles and techniques of ALE, and then we focus on studies where it has been applied to bacteria, fungi and microalgae, aiming to improve their performance to biotechnological procedures and/or inspect the genetic background of evolution. We conclude that ALE is a promising and efficacious method that has already led to the acquisition of useful new microbiological strains in biotechnology and could possibly offer even more interesting results in the future.

Economics of Biofuel Production: A Case of Sorghum and Pearl Millet in India

Reduction of fossil fuels at an alarming rate has attracted increasing attention to blending biofuels worldwide. India's energy demand is expected to grow at an annual rate of 4-5 times over the next couple of decades. With self-sufficiency levels in crude oil becoming a distant dream, there is growing interest to look out for alternative fuels and the biofuels are an important option for policy makers in India. In this context, this paper reviews the experiences in India in the last two decades with respect to biofuel cultivation and its impact on land use, environment, and the livelihoods of rural communities. The objective of this paper is to assess the economics of biofuel production using Sorghum and Pearl millet feedstocks in India using a Life Cycle Analysis (LCA) approach. Baseline study was conducted during the year 2013 in the Madhya Pradesh state of India covering five districts and 333 sample farmers to understand the farmers perception about the various issues related to the production of biofuels using Indian staple food crops Sorghum and Pearl millet. Empirical data from the multi-locational trials conducted during the years 2014-2015 and 2015-2016 in farmers' fields was used to conduct the LCA analysis. Sorghum and Pearl millet feedstocks which are rain-fed crops are considered for bioethanol production with different pretreatment methods. Net Energy Ratio (NER), Net Energy Balance (NEB), Net Carbon Balance (NCB), and % Carbon reduction were some of the key parameters used for analysis and the results are evaluated based on the environmental impacts through the Life Cycle Assessment at 5% blending. Findings reveal that, dilute alkali pretreatment process is most energy intensive due to consumption of alkali consumption. Whereas dilute acid pretreatment has higher conversion efficiency than the other pretreatment processes which is due to higher glucan and xylan conversion efficiencies.The study concludes that Sorghum feedstock is more energy intensive than Pearl millet feedstock due to higher water requirement and yield. Biofuels, either conventional or advanced, should not been couraged without a comprehensive outlook on the overall impact that will ultimately have on the society, environment, or on the countries' energy security. Efforts should be made toward encouragement of research and development in the field as well as in formulating a comprehensive and effective biofuel policy for India.

Bioethanol Production from Azolla filiculoides by Saccharomyces cerevisiae, Pichia stipitis, Candida lusitaniae, and Kluyveromyces marxianus

Ethanol was produced by separate hydrolysis and fermentation using Azolla filiculoides as a biomass. Thermal acid hydrolysis and enzymatic saccharification were used as pretreatment methods to produce monosaccharides from Azolla. The optimal content for thermal acid hydrolysis of 14% (w/v) Azolla weed slurry produced 16.7-g/L monosaccharides by using 200 mM H₂SO₄ at 121 °C for 60 min. Enzymatic saccharification using 16 U/mL Viscozyme produced 61.6 g/L monosaccharide at 48 h. Ethanol productions with ethanol yield coefficients from Azolla weed hydrolysate using Kluyveromyces marxianus, Candida lusitaniae Saccharomyces cerevisiae, and Pichia stipitis were 26.8 g/L (Y_EtOH = 0.43), 23.2 g/L (Y_EtOH = 0.37), 18.2 g/L (Y_EtOH = 0.29), and 13.7 g/L (Y_EtOH = 0.22), respectively. Saccharomyces cerevisiae produces the lowest yield as it utilized only glucose. Bioethanol from Azolla weed hydrolysate can be successfully produced by using Kluyveromyces marxianus because it consumed the mixture of glucose and xylose completely within 60 h.

Conservation of Xylose Fermentability in Phlebia Species and Direct Fermentation of Xylan by Selected Fungi

In efforts to lower the cost of total conversion of lignocellulosic materials, utilization of hemicellulose must be considered. White-rot fungus Phlebia sp. MG-60 can produce ethanol directly from cellulose and has fermentation ability for glucose, cellulose, and xylose. Therefore, white-rot fungi can be considered a good candidate for consolidated bioprocessing to give bioethanol from lignocellulosic biomass, although little information is available on the direct fermentation of xylan. In the present study, some Phlebia species were selected as candidates because of their ability to ferment xylose to ethanol more efficiently than Phlebia sp. MG-60. This process indicated that the basidiomycetes that can produce ethanol from xylose are closely related genetically within the Phlebia genus. The selected Phlebia species showed higher ethanol productivity from corn core and beechwood xylans than Phlebia sp. MG-60. The ethanol yields from corn core xylan in culture with Phlebia acerina HHB11146, Phlebia ludoviciana HHB9640, and Phlebia subochracea HHB8494 were 46.2%, 46.7%, and 39.7% of theoretical maximum, and those from beechwood xylan were 19.09%, 17.7%, and 21.4% of the theoretical maximum, respectively.

A holistic zero waste biorefinery approach for macroalgal biomass utilization: A review

The growing concerns over the depleting fossil fuels and increase in the release of greenhouse gas emissions have necessitated the search for the potential biomass source for alternative energy generation. In this context, third generation biomass specifically maroalgae has gained a lot of research interest in the recent years for energy and products generation such as ethanol, butanol, alginates, agars, and carrageenans. There are a few reviews available in scientific domain on macroalgal biomass utilization for bioethanol production but none of them has addressed precisely from phenolic precursor compounds to the entire ethanol production process and its bottlenecks. Here, we explained critically the processes involved in bioethanol, value added products and chemicals production utilizing macroalgal biomass as a feedstock along with its zero waste feasibility approach. Apart from this, we have also summarized the major issues linked to the macroalgae based biofuels and bioproducts generation processes and their possible corrective measures. Biorefinery is a promising way to generate multiple products from a single source with short processing time. Thus, this review also focuses on the recent advancement in the macroalgal biomass scaling up and how this could help in the growth of macroalgal biorefinery industry in the near future.

Production of Lactic Acid from Seaweed Hydrolysates via Lactic Acid Bacteria Fermentation

Biodegradable polylactic acid material is manufactured from lactic acid, mainly produced by microbial fermentation. The high production cost of lactic acid still remains the major limitation for its application, indicating that the cost of carbon sources for the production of lactic acid has to be minimized. In addition, a lack of source availability of food crop and lignocellulosic biomass has encouraged researchers and industries to explore new feedstocks for microbial lactic acid fermentation. Seaweeds have attracted considerable attention as a carbon source for microbial fermentation owing to their non-terrestrial origin, fast growth, and photoautotrophic nature. The proximate compositions study of red, brown, and green seaweeds indicated that Gracilaria sp. has the highest carbohydrate content. The conditions were optimized for the saccharification of the seaweeds, and the results indicated that Gracilaria sp. yielded the highest reducing sugar content. Optimal lactic acid fermentation parameters, such as cell inoculum, agitation, and temperature, were determined to be 6% (v/v), 0 rpm, and 30 °C, respectively. Gracilaria sp. hydrolysates fermented by lactic acid bacteria at optimal conditions yielded a final lactic acid concentration of 19.32 g/L.

Bioethanol Production from UK Seaweeds: Investigating Variable Pre-treatment and Enzyme Hydrolysis Parameters

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 pre-treated 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 pre-treatments are effective for seaweed biomass, yet bioethanol production alone may not make such bio-processes economically viable at large scale.

Characterization of a bifunctional alginate lyase as a new member of the polysaccharide lyase family 17 from a marine strain BP-2

OBJECTIVES

Bifunctional alginate lyase can efficiently saccharify alginate biomass and prepare functional oligosaccharides of alginate.

RESULTS

A new BP-2 strain that produces alginate lyase was screened and identified from rotted Sargassum. A new alginate lyase, Alg17B, belonging to the polysaccharide lyase family 17, was isolated and purified from BP-2 fermentation broth by freeze-drying, dialysis, and ion exchange chromatography. The enzymatic properties of the purified lyase were investigated. The molecular weight of Alg17B was approximately 77 kDa, its optimum reaction temperature was 40-45 °C, and its optimum reaction pH was 7.5-8.0. The enzyme was relatively stable at pH 7.0-8.0, with a temperature range of 25-35 °C, and the specific activity of the purified enzyme reached 4036 U/mg. A low Na+ concentration stimulated Alg17B enzyme activity, but Ca2+, Zn2+, and other metal ions inhibited it. Substrate specificity analysis, thin-layer chromatography, and mass spectrometry showed that Alg17B is an alginate lyase that catalyses the hydrolysis of sodium alginate, polymannuronic acid (polyM) and polyguluronic acid to produce monosaccharides and low molecular weight oligosaccharides. Alg17B is also bifunctional, exhibiting both endolytic and exolytic activities toward alginate, and has a wide substrate utilization range with a preference for polyM.

CONCLUSIONS

Alg17B can be used to saccharify the main carbohydrate, alginate, in the ethanolic production of brown algae fuel as well as in preparing and researching oligosaccharides.

Butanol and butyric acid production from Saccharina japonica by Clostridium acetobutylicum and Clostridium tyrobutyricum with adaptive evolution

Optimal conditions of hyper thermal (HT) acid hydrolysis of the Saccharina japonica was determined to a seaweed slurry content of 12% (w/v) and 144 mM H2SO4 at 160 °C for 10 min. Enzymatic saccharification was carried out at 50 °C and 150 rpm for 48 h using the three enzymes at concentrations of 16 U/mL. Celluclast 1.5 L showed the lowest half-velocity constant (Km) of 0.168 g/L, indicating a higher affinity for S. japonica hydrolysate. Pretreatment yielded a maximum monosaccharide concentration of 36.2 g/L and 45.7% conversion from total fermentable monosaccharides of 79.2 g/L with 120 g dry weight/L S. japonica slurry. High cell densities of Clostridium acetobutylicum and Clostridium tyrobutyricum were obtained using the retarding agents KH2PO4 (50 mM) and NaHCO3 (200 mM). Adaptive evolution facilitated the efficient use of mixed monosaccharides. Therefore, adaptive evolution and retarding agents can enhance the overall butanol and butyric acid yields from S. japonica.

Brown and Red Seaweeds Serve as Potential Efflux Pump Inhibitors for Drug-Resistant Escherichia coli

Multidrug-resistant pathogens are a significant clinical problem. Efflux pump inhibitors (EPIs) can restore the activities of existing antibiotics by interfering with drug efflux pumps located in bacterial cell membranes. Seaweeds are important sources of biologically active metabolites of natural origin; however, their potential as EPIs remains uninvestigated. Here, functional extracts from the brown seaweeds Laminaria japonica and Sargassum horneri and the red seaweeds Gracilaria sp. and Porphyra dentata were evaluated as potential EPIs against drug-resistant Escherichia coli. All these extracts were found to potentiate the activities of drugs in modulation tests, although not to the same extent. Synergistic effects of the extracts and the drug clarithromycin were observed from the onset of Time-kill assays, with no evidence of bacterial regrowth. Ethidium bromide accumulation studies revealed that the efflux decreased in the presence of each extract, as indicated by the presence of EPIs. Most identified EPIs that have been discovered to date have aromatic structures, and the seaweed extracts were found to contain various terpenes, terpenoids, phenolic compounds, indoles, pyrrole derivatives, alkaloids, and halogenated aromatic compounds. Our study highlights the potential of these compounds of the seaweeds as drug EPIs.

A Microtube Array Membrane (MTAM) Encapsulated Live Fermenting Staphylococcus epidermidis as a Skin Probiotic Patch against Cutibacterium acnes

Antibiotics without selectivity for acne treatment may destroy the beneficial microbes in the human microbiome that helps to fight Cutibacterium acnes (C. acnes), a bacterium associated with inflammatory acne vulgaris. Probiotic treatment by direct application of live Staphylococcus epidermidis (S. epidermidis) onto the open acne lesions may run the risk of bloodstream infections. Here, we fabricated the polysulfone microtube array membranes (PSF MTAM) to encapsulate probiotic S.epidermidis. We demonstrate that the application of the encapsulation of S. epidermidis in PSF MTAM enhanced the glycerol fermentation activities of S. epidermidis. To mimic the granulomatous type of acne inflammatory acne vulgaris, the ears of mice were injected intradermally with C. acnes to induce the secretion of macrophage inflammatory protein-2 (MIP-2), a murine counterpart of human interleukin (IL)-8. The C. acnes-injected mouse ears were covered with a PST MTAM encapsulated with or without S.epidermidis in the presence of glycerol. The application of S.epidermidis-encapsulated PST MTAM plus glycerol onto the C. acnes-injected mouse ears considerably reduced the growth of C. acnes and the production of MIP-2. Furthermore, no S. epidermidis leaked from PSF MTAM into mouse skin. The S. epidermidis-encapsulated PST MTAM functions as a probiotic acne patch.

Integration of protein extraction with a stream of byproducts from marine macroalgae: A model forms the basis for marine bioeconomy

The present study describes an advanced biorefinery model for marine macroalgae that assumes significant importance in the context of marine bio-economy. The method investigated in this study integrates the extraction of crude proteins with recovery of minerals rich sap, lipids, ulvan and cellulose from fresh biomass of Ulva lactuca. The protein content extracted was 11±2.12% on dry weight basis with recovery efficiency of 68.75±4.01%. The amino acid composition of crude protein fraction showed iso-leucine as the most abundant amino acid with 16.51±0.03% followed by histidine, arginine, tyrosine, serine, aspartic acid, threonine, phenyl alanine, leucine, alanine, lysine, glycine and glutamic acid (0.22±0.24%). The digestibility of protein was as high as 85.86±5.92% indicating its suitability for use in food supplements. The protein production with co-recovery of other products would not only result in effective utilisation marine macroalgal resources but also forms the basis for marine bio-economy.

Marine Enzymes and Microorganisms for Bioethanol Production

Bioethanol is a potential alternative fuel to fossil fuels. Bioethanol as a fuel has several economic and environmental benefits. Though bioethanol is produced using starch and sugarcane juice, these materials are in conflict with food availability. To avoid food-fuel conflict, the second-generation bioethanol production by utilizing nonfood lignocellulosic materials has been extensively investigated. However, due to the complexity of lignocellulose architecture, the process is complicated and not economically competitive. The cultivation of lignocellulosic energy crops indirectly affects the food supplies by extensive land use. Marine algae have attracted attention to replace the lignocellulosic feedstock for bioethanol production, since the algae grow fast, do not use land, avoid food-fuel conflict and have several varieties to suit the cultivation environment. The composition of algae is not as complex as lignocellulose due to the absence of lignin, which renders easy hydrolysis of polysaccharides to fermentable sugars. Marine organisms also produce cold-active enzymes for hydrolysis of starch, cellulose, and algal polysaccharides, which can be employed in bioethanol process. Marine microoorganisms are also capable of fermenting sugars under high salt environment. Therefore, marine biocatalysts are promising for development of efficient processes for bioethanol production.

Isolation of a novel alginate lyase-producing Bacillus litoralis strain and its potential to ferment Sargassum horneri for biofertilizer

Algae have long been used to augment plant productivity through their beneficial effects. Alginate oligosaccharide is believed to be one of the important components to enhance growth and crop yield. In this study, we isolated and characterized a Bacillus litoralis strain, named Bacillus M3, from decayed kelps. We further demonstrated that the M3 strain could secrete alginate lyase to degrade alginate. The crude enzyme exhibited the highest activity (33.74 U/mg) at pH 7.0 and 50°C. The M3 strain was also able to ferment the brown alga Sargassum horneri. Fermentation results revealed that a fermentation period of 8-12 hr was the best harvest time with the highest level of alginate oligosaccharides. Plant growth assay showed that the seaweed fermentation extract had an obvious promotion effect on root and seedling growth of Lycopersicon eseulentum L. Our results suggest that fermentation extract of Sargassum horneri by the novel strain of Bacillus litoralis M3 has significant development potential for biofertilizer production and agriculture application.

An integrated process for the extraction of fuel and chemicals from marine macroalgal biomass

We describe an integrated process that can be applied to biomass of the green seaweed, Ulva fasciata, to allow the sequential recovery of four economically important fractions; mineral rich liquid extract (MRLE), lipid, ulvan, and cellulose. The main benefits of our process are: a) its simplicity and b) the consistent yields obtained from the residual biomass after each successive extraction step. For example, dry Ulva biomass yields ~26% of its starting mass as MRLE, ~3% as lipid, ~25% as ulvan, and ~11% as cellulose, with the enzymatic hydrolysis and fermentation of the final cellulose fraction under optimized conditions producing ethanol at a competitive 0.45 g/g reducing sugar. These yields are comparable to those obtained by direct processing of the individual components from primary biomass. We propose that this integration of ethanol production and chemical feedstock recovery from macroalgal biomass could substantially enhance the sustainability of marine biomass use.

Potential of phosphoric acid-catalyzed pretreatment and subsequent enzymatic hydrolysis for biosugar production from Gracilaria verrucosa

This study combined phosphoric acid-catalyzed pretreatment and enzymatic hydrolysis to produce biosugars from Gracilaria verrucosa as a potential renewable resource for bioenergy applications. We optimized phosphoric acid-catalyzed pretreatment conditions to 1:10 solid-to-liquid ratio, 1.5 % phosphoric acid, 140 °C, and 60 min reaction time, producing a 32.52 ± 0.06 % total reducing sugar (TRS) yield. By subsequent enzymatic hydrolysis, a 68.61 ± 0.90 % TRS yield was achieved. These results demonstrate the potential of phosphoric acid to produce biosugars for biofuel and biochemical production applications.

Bioethanol production from taro waste using thermo-tolerant yeast Kluyveromyces marxianus K21

In the present study, evaluation and optimization of taro waste (TW), which was mainly composed of taro peels that contain many starch residues, as the main carbon source in medium were studied. The flask studies showed the optimal medium was using 170g/L of TW which is about 100g/L of glucose and 9g/L of CGM as alternative nitrogen source. Simultaneous saccharification and fermentation (SSF) exhibited higher bioethanol productivity toward separation hydrolysis and fermentation (SHF). The optimal condition of SSF was 5% of Kluyveromyces marxianus K21 inoculum at 40°C resulting in the maximum ethanol concentration (48.98g/L) and productivity (2.23g/L/h) after 22h of cultivation. The scaling up experiment in a 5L bioreactor demonstrated that K21 can still maintain its capability. After 20h of cultivation, 43.78g/L of ethanol (2.19g/L/h of productivity) was achieved corresponding to a 94.2% theoretical ethanol yield.

Direct bioconversion of brown algae into ethanol by thermophilic bacterium Defluviitalea phaphyphila

BACKGROUND

Brown algae are promising feedstocks for biofuel production with inherent advantages of no structural lignin, high growth rate, and no competition for land and fresh water. However, it is difficult for one microorganism to convert all components of brown algae with different oxidoreduction potentials to ethanol. Defluviitalea phaphyphila Alg1 is the first characterized thermophilic bacterium capable of direct utilization of brown algae.

RESULTS

Defluviitalea phaphyphila Alg1 can simultaneously utilize mannitol, glucose, and alginate to produce ethanol, and high ethanol yields of 0.47 g/g-mannitol, 0.44 g/g-glucose, and 0.3 g/g-alginate were obtained. A rational redox balance system under obligate anaerobic condition in fermenting brown algae was revealed in D. phaphyphila Alg1 through genome and redox analysis. The excess reducing equivalents produced from mannitol metabolism were equilibrated by oxidizing forces from alginate assimilation. Furthermore, D. phaphyphila Alg1 can directly utilize unpretreated kelp powder, and 10 g/L of ethanol was accumulated within 72 h with an ethanol yield of 0.25 g/g-kelp. Microscopic observation further demonstrated the deconstruction process of brown algae cell by D. phaphyphila Alg1.

CONCLUSIONS

The integrated biomass deconstruction system of D. phaphyphila Alg1, as well as its high ethanol yield, provided us an excellent alternative for brown algae bioconversion at elevated temperature.

High-yield production of biosugars from Gracilaria verrucosa by acid and enzymatic hydrolysis processes

Gracilaria verrucosa, the red alga, is a suitable feedstock for biosugar production. This study analyzes biosugar production by the hydrolysis of G. verrucosa conducted under various conditions (i.e., various acid concentrations, substrate concentrations, reaction times, and enzyme dosages). The acid hydrolysates of G. verrucosa yielded a total of 7.47g/L (37.4%) and 10.63g/L (21.26%) of reducing sugars under optimal small (30mL) and large laboratory-scale (1L) hydrolysis processes, respectively. Reducing sugar obtained from acid and enzymatic hydrolysates were 10% higher, with minimum by-products, than those reported in other studies. The mass balance for the small laboratory-scale process showed that the acid and enzymatic hydrolysates had a carbohydrate conversion of 57.2%. The mass balance approach to the entire hydrolysis process of red seaweed for biosugar production can be applied to other saccharification processes.