Biogas production and saccharification of Salix pretreated at different steam explosion conditions

Different steam explosion conditions were applied to Salix chips and the effect of this pretreatment was evaluated by running both enzymatic hydrolysis and biogas tests. Total enzymatic release of glucose and xylose increased with pretreatment harshness, with maximum values being obtained after pretreatment for 10 min at 210 °C. Harsher pretreatment conditions did not increase glucose release, led to degradation of xylose and to formation of furfurals. Samples pretreated at 220 and 230 °C initially showed low production of biogas, probably because of inhibitors produced during the pretreatment, but the microbial community was able to adapt and showed high final biogas production. Interestingly, final biogas yields correlated well with sugar yields after enzymatic hydrolysis, suggesting that at least in some cases a 24 h enzymatic assay may be developed as a quick method to predict the effects of pretreatment of lignocellulosic biomass on biogas yields.     

Comparative biochemical analysis during the anaerobic digestion of lignocellulosic biomass from six morphological parts of Williams Cavendish banana (Triploid Musa AAA group) plants

We studied banana lignocellulosic biomass (BALICEBIOM) that is abandoned after fruit harvesting, and assessed its biochemical methane potential, because of its potential as an energy source. We monitored biogas production from six morphological parts (MPs) of the “Williams Cavendish” banana cultivar using a modified operating procedure (KOP) using KOH. Volatile fatty acid (VFA) production was measured using high performance liquid chromatography. The bulbs, leaf sheaths, petioles–midribs, leaf blades, rachis stems, and floral stalks gave total biogas production of 256, 205, 198, 126, 253, and 221 ml g^?1 dry matter, respectively, and total biomethane production of 150, 141, 127, 98, 162, and 144 ml g^?1, respectively. The biogas production rates and yields depended on the biochemical composition of the BALICEBIOM and the ability of anaerobic microbes to access fermentable substrates. There were no significant differences between the biogas analysis results produced using KOP and gas chromatography. Acetate was the major VFA in all the MP sample culture media. The bioconversion yields for each MP were below 50 %, showing that these substrates were not fully biodegraded after 188 days. The estimated electricity that could be produced from biogas combustion after fermenting all of the BALICEBIOM produced annually by the Cameroon Development Corporation–Del Monte plantations for 188 days is approximately 10.5 × 10⁶ kW h (which would be worth 0.80–1.58 million euros in the current market). This bioenergy could serve the requirements of about 42,000 people in the region, although CH₄ productivity could be improved.     

Biodegradation of Cellulose-Containing Substrates by Micromycetes Followed by Bioconversion into Biogas

The ability of micromycetes Trichoderma viride and Aspergillus terreus to decompose the cellulosecontaining substrates was studied. Office paper and cardboard, as well as a paper mixture, were found to be the most hydrolyzable. The cellulolytic activity of T. viride was 2–3 times higher than that of A. terreus; the highest values of 0.80 and 0.73 U/mL were obtained from office paper and the mixture of different types of paper, respectively. The micromycete cultivation conditions (composition of culture medium, sucrose cosubstrate addition, seeding technique) and the conditions of the fungus biomass treatment for its subsequent bioconversion into biogas by anaerobic microbial communities were optimized. It was shown that pretreatment improves the efficiency of biogas production from lignocellulosic materials when inoculated with microbial community of cattle manure. After pretreatment of the Jerusalem artichoke phytomass (stems and leaves) and its subsequent bioconversion into biogas by methanogenic community, the biogas yield was increased by1.5 times.     

Optimisation of the biological pretreatment of wheat straw with white-rot fungi for ethanol production

The biological pretreatment of lignocellulosic biomass for the production of bioethanol is an environmentally friendly alternative to the most frequently used process, steam explosion (SE). However, this pretreatment can still not be industrially implemented due to long incubation times. The main objective of this work was to test the viability of and optimise the biological pretreatment of lignocellulosic biomass, which uses ligninolytic fungi (Pleurotus eryngii and Irpex lacteus) in a solid-state fermentation of sterilised wheat straw complemented with a mild alkali treatment. In this study, the most important parameters of the mechanical and thermal substrate conditioning processes and the most important parameters of the fungal fermentation process were optimised to improve sugar recovery. The largest digestibilities were achieved with fermentation with I. lacteus under optimised conditions, under which cellulose and hemicellulose digestibility increased after 21 days of pretreatment from 16 to 100 % and 12 to 87 %, respectively. The maximum glucose yield (84 %) of cellulose available in raw material was obtained after only 14 days of pretreatment with an overall ethanol yield of 74 % of the theoretical value, which is similar to that reached with SE.     

Immobilized anaerobic fermentation for bio-fuel production by Clostridium co-culture

Clostridium thermocellum/Clostridium thermolacticum co-culture fermentation has been shown to be a promising way of producing ethanol from several carbohydrates. In this research, immobilization techniques using sodium alginate and alkali pretreatment were successfully applied on this co-culture to improve the bio-ethanol fermentation performance during consolidated bio-processing (CBP). The ethanol yield obtained increased by over 60 % (as a percentage of the theoretical maximum) as compared to free cell fermentation. For cellobiose under optimized conditions, the ethanol yields were approaching about 85 % of the theoretical efficiency. To examine the feasibility of this immobilization co-culture on lignocellulosic biomass conversion, untreated and pretreated aspen biomasses were also used for fermentation experiments. The immobilized co-culture shows clear benefits in bio-ethanol production in the CBP process using pretreated aspen. With a 3-h, 9 % NaOH pretreatment, the aspen powder fermentation yields approached 78 % of the maximum theoretical efficiency, which is almost twice the yield of the untreated aspen fermentation.     

Comparative study on the mycelial growth and yield of Ganoderma lucidum (Curt.: Fr.) Karst. on different lignocellulosic wastes

The aim of this study was to examine the possibility of using wheat straw (WS), cottonseed meal (CSM), sunflower meal (SFM), soybean straw (SBS) and bean straw (BS) as basal substrates in Ganoderma lucidum cultivation instead of oak (OS) and poplar (PS) sawdusts. In the study, effects of different growing substrates on spawn running period, yield and biological efficiency (BE) of G. lucidum were determined. Moreover, possible correlations among productivity and lignocellulosic content of substrates were assessed. Average spawn run period varied between 14.2 and 18.2 d. Total yields of G. lucidum grown on different substrates ranged from 28.6 g/kg to 86.1 g/kg, while the corresponding values for BE varied between 8.9%–24.7%. The highest yield and BE was exhibited by the OS followed by PS substrate. CSM gave the lowest yield and BE. Spawn running time was found to be positively correlated to nitrogen content of the substrates (r² = 0.918) and negatively correlated to cellulose and hemicellulose content of substrate (r² = −0.927 and r² = −0.838, respectively). The total mushroom yield was correlated negatively to nitrogen content of the substrates (r² = −0.850) and positively correlated to C:N ratio (r²=0.915). Moreover, there is a strong positive correlation between mushroom yield and cellulose and lignin content of the substrates (r² = 0.794 and r²= 0.879). According to results, G. lucidum had a preference for substrates containing a high amount of cellulose and and lignin, and having a low amount of N and high cellulose:lignin ratio. Furthermore, SBS, WS and BS may be suggested as alternative basal substrates for cultivation of G. lucidum.     

Lignocellulose conversion for biofuel: a new pretreatment greatly improves downstream biocatalytic hydrolysis of various lignocellulosic materials

Background

Lignocellulosic biomass is an attractive renewable resource for future liquid transport fuel. Efficient and cost-effective production of bioethanol from lignocellulosic biomass depends on the development of a suitable pretreatment system. The aim of this study is to investigate a new pretreatment method that is highly efficient and effective for downstream biocatalytic hydrolysis of various lignocellulosic biomass materials, which can accelerate bioethanol commercialization.

Results

The optimal conditions for the hydrogen peroxide–acetic acid (HPAC) pretreatment were 80 °C, 2 h, and an equal volume mixture of H₂O₂ and CH₃COOH. Compared to organo-solvent pretreatment under the same conditions, the HPAC pretreatment was more effective at increasing enzymatic digestibility. After HPAC treatment, the composition of the recovered solid was 74.0 % cellulose, 20.0 % hemicelluloses, and 0.9 % lignin. Notably, 97.2 % of the lignin was removed with HPAC pretreatment. Fermentation of the hydrolyzates by S. cerevisiae resulted in 412 mL ethanol kg^?1 of biomass after 24 h, which was equivalent to 85.0 % of the maximum theoretical yield (based on the amount of glucose in the raw material).

Conclusion

The newly developed HPAC pretreatment was highly effective for removing lignin from lignocellulosic cell walls, resulting in enhanced enzymatic accessibility of the substrate and more efficient cellulose hydrolysis. This pretreatment produced less amounts of fermentative inhibitory compounds. In addition, HPAC pretreatment enables year-round operations, maximizing utilization of lignocellulosic biomass from various plant sources.

     

Biomass yield and morphological features of the seaweed Saccharina latissima cultivated at two different sites in a coastal bay in the Atlantic coast of Spain

The kelp Saccharina latissima is an economically important edible seaweed with great potential for use in other applications. The goal of this study was to identify locations in a coastal bay with better conditions for commercial cultivation of this species. We compared the biomass yield and morphological features of S. latissima cultivated at two locations in a bay of Galicia (northwest Spain): in an external moderately exposed site and in an internal sheltered site. Biomass yield was significantly higher at the moderately exposed site than at the sheltered site (16 fresh kg vs. 12 fresh kg per linear meter of rope). Fronds were significantly larger at the moderately exposed site compared to that at the sheltered site. However, the “substantiality value” (around 40 mg cm^?2), which is an index used to assess blade quality for human consumption, did not differ significantly between the two locations. The effect of light exposure and water velocity seemed to be the most important environmental factors that explain the differences in the results obtained at both culture sites. In summary, both the moderately exposed site and the sheltered site were suitable for cultivation of S. latissima, as indicated by the high yields and similar blade quality obtained at both locations.     

Pretreatment of pulp mill secondary sludge for high-rate anaerobic conversion to biogas

Three pretreatment methods were compared based on their ability to increase the extent and rate of anaerobic bioconversion of pulp mill secondary sludge to biogas. The pretreatment technologies used in these experiments were: (i) thermal pretreatment performed at 170 °C; (ii) thermochemical (caustic) pretreatment performed at pH 12 and 140 °C; and (iii) sonication performed at 20 kHz and 1 W mL⁻¹. Sludge samples were obtained from a sulfite and a kraft pulp mill, and biochemical methane potential (BMP) assays were performed using microbial granules obtained from a high-rate anaerobic digester operating at a pulp mill. Biogas production from untreated sludge was 0.05 mL mg⁻¹ of measured chemical oxygen demand (COD) and 0.20 mL mg⁻¹ COD for kraft and sulfite sludge, respectively. Thermal pretreatment had the highest impact on sludge biodegradability. In this case, biogas yield and production rate from sulfite sludge increased by 50% and 10 times, respectively, while biogas yield and production rate from kraft sludge increased by 280% and 300 times, respectively. Biogas yield correlated to soluble carbohydrate content better than soluble COD.     

Production of optically pure <Emphasis Type="SmallCaps">l</Emphasis>(+)-lactic acid from waste plywood chips using an isolated thermotolerant <Emphasis Type="Italic">Enterococcus faecalis</Emphasis> SI at a pilot scale

Utilization of renewable and low-cost lignocellulosic wastes has received major focus in industrial lactic acid production. The use of high solid loadings in biomass pretreatment potentially offers advantages over low solid loadings including higher lactic acid concentration with decreased production and capital costs. In this study, an isolated Enterococcus faecalis SI with optimal temperature 42 °C was used to produce optically pure l-lactic acid (>?99%) from enzyme-saccharified hydrolysates of acid-impregnated steam explosion (AISE)-treated plywood chips. The l-lactic acid production increased by 10% at 5 L scale compared to the similar fermentation scheme reported by Wee et al. The fermentation with a high solid loading of 20% and 35% (w/v) AISE-pretreated plywood chips had been successfully scaled up to process development unit scale (100 L) and pilot scale (9 m³), respectively. This is the first report of pilot-scale lignocellulosic lactic acid fermentation by E. faecalis with high lactic acid titer (nearly 92 g L^?1) and yield (0.97 kg kg^?1). Therefore, large-scale l-lactic acid production by E. faecalis SI shows the potential application for industries.     

Impact of pretreatment on solid state anaerobic digestion of yard waste for biogas production

Solid state anaerobic digestion, as a safe and environment-friendly technology to dispose municipal solid wastes, can produce methane and reduce the volume of wastes. In order to raise the digestion efficiency, this study investigated the pretreatment of yard waste by thermal or chemical method to break down the complex lignocellulosic structure. The composition and structure of pretreated yard waste were analyzed and characterized. The results showed that the pretreatment decreased the content of cellulose and hemicelluloses in yard waste and in turn improved the hydrolysis and methanogenic processes. The thermal pretreatment sample (P1) had the highest methane yield, by increasing 88 % in comparison with digesting the raw material. The maximum biogas production reached 253 mL/g volatile solids (VS). The largest substrate mass reduction was obtained by the alkaline pretreatment (P5). The VS of the alkaline-treated sample decreased about 60 % in comparison with the raw material.     

Assimilation of inorganic nutrients from salmon (Salmo salar) farming by the macroalgae (Saccharina latissima) in an exposed coastal environment: implications for integrated multi-trophic aquaculture

This paper investigated the assimilation of dissolved inorganic nitrogen (DIN) in Saccharina latissima in proximity to salmon cages in coastal waters. The bioassays were performed on plants from three stations located in the vicinity of a salmon farm (Salmo salar) in exposed waters at Tristein (63° 52′ N, 9° 37′ E) in Central Norway. The growth, the C and N content, and the nitrogen isotope ratios (δ¹⁵N) of S. latissima were monitored over 1 year. The DIN concentrations in seawater were higher at the salmon farm stations than at the reference station during the winter, and the N/P ratio at the salmon farm stations was higher from September to January and in June. S. latissima at the salmon farm stations grew faster than at the reference station. The length of S. latissima increased by 50 % when integrated with the salmon farm compared to the reference station. The N content of S. latissima was positively correlated to the DIN concentration in seawater (p?<?0.05), but the increased N supply from salmon did not result in N accumulation in S. latissima at the salmon farm station because of the dilution by a higher growth rate. The δ¹⁵N in S. latissima was higher at the salmon farm station from April to June and changed in the direction of the δ¹⁵N signature in urine. This indicated that N in S. latissima at the salmon farm station partly originated from the salmon. One hectare of S. latissima may absorb 0.8～1.2 t N during one growth season. Large-scale cultivation of S. latissima should be considered to mitigate the environmental effects of DIN wastes from salmon farms.     

Enhancing anaerobic biogasification of corn stover through wet state NaOH pretreatment

A new method of wet state (WS) sodium hydroxide (NaOH) was advanced to pretreat corn stover for enhancing biogas production. The results showed that 88% moisture content, 3-day treatment time and ambient temperature (20 °C) was appropriate for WS NaOH pretreatment. The NaOH dose of 2% and the loading rate of 65 g/L were found to be optimal in terms of 72.9% more total biogas production, 73.4% more methane yield, and 34.6% shorter technical digestion time, as compared to the untreated one. WS pretreatment used 86% shorter treatment time and 66.7% less NaOH dose than solid state one. The analyses of chemical compositions and chemical structures showed that 9.3–19.1% reduction of the contents of total Lignin, cellulose, and hemicellulose (LCH), and 27.1–77.1% increase of hot-water extractives contributed to the enhancement of biogas production. WS NaOH pretreatment could be one of cost-effective methods for high efficient biological conversion of corn stover into bioenergy.     

Biogas properties and enzymatic analysis during anaerobic fermentation of <Emphasis Type="Italic">Phragmites australis</Emphasis> straw and cow dung: influence of nickel chloride supplement

The importance of nickel (added as NiCl₂) on mesophilic anaerobic fermentation of Phragmites australis straw and cow dung was demonstrated by investigating the biogas properties, pH values, organic matter degradation [chemical oxygen demand (COD)] and enzyme activities (cellulase, protease and dehydrogenase) during the fermentation process. The results showed that Ni²⁺ addition increased the cumulative biogas yields by >18 % by improving the efficiency of first peak stage and bringing forward the second peak stage. The pH values were not significantly influenced by Ni²⁺ addition (p > 0.05). Biogas yields were associated with variations in COD concentrations rather than momentary concentrations. At the start-up stage of fermentation (4th day), the biogas yields increased gradually together with the increase of dehydrogenase activities at elevated Ni²⁺ concentrations when cellulase and protease activities were similar in all test groups. It is suggested that Ni²⁺ addition was mainly dependent on the methanogenic stage. After the start-up stage, the impact of Ni²⁺ addition on biogas production was mainly dependent on its effect on cellulase activities, rather than protease or dehydrogenase activities.     

Switchgrass Biofuel Production on Reclaimed Surface Mines: II. Feedstock Quality and Theoretical Ethanol Production

Switchgrass (Panicum virgatum L.), a warm-season perennial grass, is an important bioenergy crop candidate because it produces high biomass yields on marginal lands and on reclaimed surface mined sites. In companion studies, dry matter (DM) yields for Cave-in-Rock, Shawnee, and Carthage cultivars varied from 4.2 to 13.0 Mg ha^?1averaged over 6 years at the reclaimed Hampshire site, and fertilization increased yields of Cave-in-Rock at Black Castle and Coal Mac sites from 0.3 to 2 Mg ha^?1 during the first 3 years. The objective of these experiments was to compare the impacts of cultivar and soil amendments on biomass quality and theoretical ethanol production of switchgrass grown on surface mines with differing soil characteristics. Biomass quality was determined for fiber, ash, lignin, digestibility, and carbohydrate contents via near-infrared reflectance spectroscopy, and carbohydrates were used to calculate theoretical ethanol yield (TEY; L Mg^?1) and multiplied by biomass yield to calculate theoretical ethanol production (TEP; L ha^?1). Cultivars at the Hampshire site did not differ in TEY and ranged from 426 to 457 L Mg^?1. Theoretical ethanol production from Cave-in-Rock at Hampshire was 7350 L ha^?1, which was higher than other cultivars because of its greater biomass production. This TEP was higher than in other studies which predicted 4000 to 5000 L ha^?1. At the Black Castle and Coal Mac sites, fertilizer applications slightly affected biomass quality of switchgrass and TEY, but provided greater TEP as a function of increased yield. Similar to other findings, total switchgrass biomass production has more impact than compositional differences on TEP, so maximizing biomass production is critical for maximizing potential biofuel production. With appropriate soil substrates, fertilization, planning, and management, large areas of reclaimed surface mines can be converted to switchgrass stands to produce high biomass quality and yields to support a bioethanol industry.     

Copper stressed anaerobic fermentation: biogas properties,process stability,biodegradation and enzyme responses

The effect of copper (added as CuCl₂) on the anaerobic co-digestion of Phragmites straw and cow dung was studied in pilot experiments by investigating the biogas properties, process stability, substrate degradation and enzyme activities at different stages of mesophilic fermentation. The results showed that 30 and 100 mg/L Cu²⁺ addition increased the cumulative biogas yields by up to 43.62 and 20.77% respectively, and brought forward the daily biogas yield peak, while 500 mg/L Cu²⁺ addition inhibited biogas production. Meanwhile, the CH₄ content in the 30 and 100 mg/L Cu²⁺-added groups was higher than that in the control group. Higher pH values (close to pH 7) and lower oxidation–reduction potential (ORP) values in the Cu²⁺-added groups after the 8th day indicated better process stability compared to the control group. In the presence of Cu²⁺, the degradation of volatile fatty acids (VFAs) and other organic molecules (represented by chemical oxygen demand, COD) generated from hydrolysis was enhanced, and the ammonia nitrogen (NH₄ ⁺-N) concentrations were more stable than in the control group. The contents of lignin and hemicellulose in the substrate declined in the Cu²⁺-added groups while the cellulose contents did not. Neither the cellulase nor the coenzyme F₄₂₀ activities could determine the biogas producing efficiency. Taking the whole fermentation process into account, the promoting effect of Cu²⁺ addition on biogas yields was mainly attributable to better process stability, the enhanced degradation of lignin and hemicellulose, the transformation of intermediates into VFA, and the generation of CH₄ from VFA.     

Cellulases from Penicillium funiculosum: production, properties and application to cellulose hydrolysis

The objective of this work is to investigate the utilization of two abundant agricultural residues in Brazil for the production and application of cellulolytic enzymes. Different materials obtained after pretreatment of sugarcane bagasse, as well as pure synthetic substrates, were considered for cellulase production by Penicillium funiculosum. The best results for FPase (354 U L^?1) and β-glucosidase (1,835 U L^?1) production were observed when sugarcane bagasse partially delignified cellulignin (PDC) was used. The crude extract obtained from PDC fermentation was then partially characterized. Optimal temperatures for cellulase action ranged from 52 to 58°C and pH values of around 4.9 contributed to maximum enzyme activity. At 37°C, the cellulases were highly stable, losing less than 15% of their initial activity after 23 h of incubation. There was no detection of proteases in the P. funiculosum extract, but other hydrolases, such as endoxylanases, were identified (147 U L^?1). Finally, when compared to commercial preparations, the cellulolytic complex from P. funiculosum showed more well-balanced amounts of β-glucosidase, endo- and exoglucanase, resulting in the desired performance in the presence of a lignocellulosic material. Cellulases from this filamentous fungus had a higher glucose production rate (470 mg L^?1 h^?1) when incubated with corn cob than with Celluclast^®, GC 220^® and Spezyme^® (312, 454 and 400 mg L^?1 h^?1, respectively).     

<Emphasis Type="Italic">Bacillus amyloliquefaciens</Emphasis> Spore Production Under Solid-State Fermentation of Lignocellulosic Residues

This study was conducted to elucidate cultivation conditions determining Bacillus amyloliquefaciens B-1895 growth and enhanced spore formation during the solid-state fermentation (SSF) of agro-industrial lignocellulosic biomasses. Among the tested growth substrates, corncobs provided the highest yield of spores (47?×?10¹⁰ spores g^?1 biomass) while the mushroom spent substrate and sunflower oil mill appeared to be poor growth substrates for spore formation. Maximum spore yield (82?×?10¹⁰ spores g^?1 biomass) was achieved when 15 g corncobs were moistened with 60 ml of the optimized nutrient medium containing 10 g peptone, 2 g KH₂PO₄, 1 g MgSO₄·7H₂O, and 1 g NaCl per 1 l of distilled water. The cheese whey usage for wetting of lignocellulosic substrate instead water promoted spore formation and increased the spore number to 105?×?10¹⁰ spores g^?1. Addition to the cheese whey of optimized medium components favored sporulation process. The feasibility of developed medium and strategy was shown in scaled up SSF of corncobs in polypropylene bags since yield of 10?×?10¹¹ spores per gram of dry biomass was achieved. In the SSF of lignocellulose, B. amyloliquefaciens B-1895 secreted comparatively high cellulase and xylanase activities to ensure good growth of the bacterial culture.     

Fermentation of lignocellulosic sugars to acetic acid by <Emphasis Type="Italic">Moorella thermoacetica</Emphasis>

A systematic study of bioconversion of lignocellulosic sugars to acetic acid by Moorella thermoacetica (strain ATCC 39073) was conducted. Four different water-soluble fractions (hydrolysates) obtained after steam pretreatment of lignocellulosic biomass were selected and fermented to acetic acid in batch fermentations. M. thermoacetica can effectively ferment xylose and glucose in hydrolysates from wheat straw, forest residues, switchgrass, and sugarcane straw to acetic acid. Xylose and glucose were completely utilized, with xylose being consumed first. M. thermoacetica consumed up to 62 % of arabinose, 49 % galactose and 66 % of mannose within 72 h of fermentation in the mixture of lignocellulosic sugars. The highest acetic acid yield was obtained from sugarcane straw hydrolysate, with 71 % of theoretical yield based on total sugars (17 g/L acetic acid from 24 g/L total sugars). The lowest acetic acid yield was observed in forest residues hydrolysate, with 39 % of theoretical yield based on total sugars (18 g/L acetic acid from 49 g/L total sugars). Process derived compounds from steam explosion pretreatment, including 5-hydroxymethylfurfural (0.4 g/L), furfural (0.1 g/L) and total phenolics (3 g/L), did not inhibit microbial growth and acetic acid production yield. This research identified two major factors that adversely affected acetic acid yield in all hydrolysates, especially in forest residues: (i) glucose to xylose ratio and (ii) incomplete consumption of arabinose, galactose and mannose. For efficient bioconversion of lignocellulosic sugars to acetic acid, it is imperative to have an appropriate balance of sugars in a hydrolysate. Hence, the choice of lignocellulosic biomass and steam pretreatment design are fundamental steps for the industrial application of this process.     

Improving biomass production and saccharification in <Emphasis Type="Italic">Brachypodium distachyon</Emphasis> through overexpression of a sucrose-phosphate synthase from sugarcane

The substitution of fossil by renewable energy sources is a major strategy in reducing CO₂ emission and mitigating climate change. In the transport sector, which is still mainly dependent on liquid fuels, the production of second generation ethanol from lignocellulosic feedstock is a promising strategy to substitute fossil fuels. The main prerequisites on designated crops for increased biomass production are high biomass yield and optimized saccharification for subsequent use in fermentation processes. We tried to address these traits by the overexpression of a sucrose-phosphate synthase gene (SoSPS) from sugarcane (Saccharum officinarum) in the model grass Brachypodium distachyon. The resulting transgenic B. distachyon lines not only revealed increased plant height at early growth stages but also higher biomass yield from fully senesced plants, which was increased up to 52 % compared to wild-type. Additionally, we determined higher sucrose content in senesced leaf biomass from the transgenic lines, which correlated with improved biomass saccharification after conventional thermo-chemical pretreatment and enzymatic hydrolysis. Combining increased biomass production and saccharification efficiency in the generated B. distachyon SoSPS overexpression lines, we obtained a maximum of 74 % increase in glucose release per plant compared to wild-type. Therefore, we consider SoSPS overexpression as a promising approach in molecular breeding of energy crops for optimizing yields of biomass and its utilization in second generation biofuel production.