Synthesis of Green Deep Eutectic Solvents for Pretreatment Wheat Straw: Enhance the Solubility of Typical Lignocellulose

Deep eutectic solvents (DESs), a novel and environmentally-friendly solvent, have high potential for biomass pretreatment due to its advantages of low cost, low toxicity, strong solubility, excellent selectivity and biocompatibility. Two types of DES (binary and ternary) were synthesized and characterized, and optimized ternary DES was selected to pretreat wheat straw for enhancement of the solubility of lignocellulose. Moreover, enzymatic hydrolysis was tested to verify the performance of pretreatment. In addition, the changes in surface morphology, structure and crystallinity of wheat straw pretreated by DES were analyzed to reveal the pretreatment mechanism. Experimental results indicated that viscosity exhibited little difference in different types of DESs, and a declining trend as the temperature increases in same DES. The ternary DES pretreatment efficiently enhanced the solubility of typical lignocellulose, with the optimal removal rate of lignin at approximately 69.46%. Furthermore, the total sugar concentration of the residue was about 5.1 times more than that of untreated wheat straw after the pretreated samples were hydrolyzed by the cellulase for 24 h, indicating that DES has the unique ability to selectively extract lignin and hemicellulose from wheat straw while retaining cellulose, and thus enhanced the solubility of lignocellulose. The scanning electron microscope (SEM) observation and X-ray diffraction (XRD) determination showed that the surface of wheat straw suffered from serious erosion and the crystallinity index of wheat straw increased after DES5 pretreatment. Therefore, DES cleaves the covalent bond between lignin and cellulose and hemicellulose, and reduces the intractability of lignin resulting in the lignin dissolution. It suggests that DES can be used as a promising and biocompatible pretreatment way for the cost-effective conversion of lignocellulose biomass into biofuels.

Aqueous Ammonia With Sodium Sulfite Pretreatment For Enhancing Enzymatic Saccharification and Bioethanol Production of Sugarcane Bagasse

Background: Bioethanol is considered as a promising alternative fuel. Lignocellulosic biomass can be used for the production of bioethanol, but its recalcitrant structure makes it difficult to be utilized. Thus, proper pretreatment is a crucial step to break this structure and enhance enzymatic saccharification. Aqueous ammonia with sodium sulfite pretreatment (AAWSSP) was first applied to enhance the enzymatic saccharification and bioethanol production of sugarcane bagasse (SCB) in this research.Results: Response surface methodology was applied to optimize the conditions of pretreatment. Under optimal parameters, 16.92 g/L of total sugar concentration (P1 SCB: 202.08℃, 11.06% aqueous ammonia, 13.37% sodium sulfite, 1.22 h) and 0.51 g/g of total sugar yield (P2 SCB: 199.47℃, 10.17% aqueous ammonia, 13.11% sodium sulfite, 1.17 h) were achieved, respectively. The results of ethanol fermentation showed that separate hydrolysis and fermentation performed better than that of simultaneous saccharification and fermentation, and the maximum ethanol yields of 143.30 g/kg for P1 SCB and 145.33 g/kg for P2 SCB, were obtained, respectively. Conclusions: This research indicated that aqueous ammonia and sodium sulfite in pretreatment solution might have a synergistic effect on delignification and enzymatic saccharification. AAWSSP might be a prospective method for enhancing enzymatic saccharification and bioethanol production of SCB, which provided new guidance for the bio-refinery of lignocellulose.

Mutagenesis of novel clostridial fusants for enhanced green biobutanol production using renewable and sustainable feedstock

Biobutanol was produced in the present work through Simultaneous Saccharification and Fermentation (SSF) of cellulosic feedstock (i.e. wheat straw (WS)) and algal biomass. Novel Clostridial fused strains developed earlier underwent mutagenesis for strain enhancement using UV and chemical mutagen (ethyl methanesulphonate). Results for mutated strains showed higher biobutanol production of 14.6 g/L, with total acetone, biobutanol and ethanol (ABE) yield of 0.6 g/g. Moreover, mutated strains showed tolerance to biobutanol toxicity at 15g/L; ~15% increase over literature values. Algal biomass was pre-treated using different thermal, chemical and enzymatic pre-treatments to define its biobutanol production potential compared to WS. A total sugar concentration of 26.4 g/L and glucose concentration of 12.48 g/L was obtained with enzymatic pre-treatment. Biobutanol production through SSF of algal biomass showed maximum concentration of biobutanol of 7.52 g/L with a total ABE yield of 0.48 g/g.

Mutagenesis of novel clostridial fusants for enhanced green biobutanol production using renewable and sustainable feedstock

Biobutanol was produced in the present work through Simultaneous Saccharification and Fermentation (SSF) of cellulosic feedstock (i.e. wheat straw (WS)) and algal biomass. Novel Clostridial fused strains developed earlier underwent mutagenesis for strain enhancement using UV and chemical mutagen (ethyl methanesulphonate). Results for mutated strains showed higher biobutanol production of 14.6 g/L, with total acetone, biobutanol and ethanol (ABE) yield of 0.6 g/g. Moreover, mutated strains showed tolerance to biobutanol toxicity at 15g/L; ~15% increase over literature values. Algal biomass was pre-treated using different thermal, chemical and enzymatic pre-treatments to define its biobutanol production potential compared to WS. A total sugar concentration of 26.4 g/L and glucose concentration of 12.48 g/L was obtained with enzymatic pre-treatment. Biobutanol production through SSF of algal biomass showed maximum concentration of biobutanol of 7.52 g/L with a total ABE yield of 0.48 g/g.

Evaluation of olive mill waste as substrate for carotenoid production by Rhodotorula mucilaginosa

The “alperujo” is a waste from the olive oil industry with great potential for valorization. It has a high organic load, with the presence of valuable compounds such as biophenols and sugars. The use of this waste can be thought of as a biorefinery from which different compounds of high added value can be obtained, whether they are present in the “alperujo” such as biophenols or can be generated from the “alperujo”. Therefore, the production of carotenoids by Rhodotorula mucilaginosa was evaluated using the liquid fraction of ‘alperujo’ (Alperujo Water, AW) or an aqueous extract (AE) of “alperujo” at different concentrations (5, 10, 20 and 30% w/V) as substrates. The AEs had an acidic pH, a total sugar concentration ranging from 1.6 to 7.6 g/L, a polyphenols content from 0.4 to 2.9 g/L and a significant amount of proteins (0.5–3 g/L). AW is similar in composition as 30% AE, but with a higher amount of total sugars. Rh. mucilaginosa was able to grow at the different mediums with consumption of glucose and fructose, a reduction in protein content and alkalinization of the medium. Maximum total carotenoid production (7.3 ± 0.6 mg/L) was achieved at AW, while the specific production was higher when the yeast grew at AW or at 30% AE (0.78 ± 0.06 and 0.73 ± 0.10 mg/g of biomass, respectively). Torulene and torularhodin were the main carotenoids produced. Polyphenol content did not change; thus, it is still possible to recover these compounds after producing carotenoids. These results demonstrate the feasibility of using alperujo-based mediums as cheap substrates to produce torularhodin and torulene and to include this bioprocess as a step in an integral approach for alperujo valorization.

Comprehensive study on the effects of process parameters of alkaline thermal pretreatment followed by thermomechanical extrusion in sugar liberation from Eucalyptus grandis wood

A combination of alkaline thermal pretreatment followed by thermomechanical extrusion was studied as a novel sequential pretreatment process for an effective breakdown of the lignocellulosic structure of Eucalyptus grandis wood (EW). The first step was studied by analysing the influence of two factors: the NaOH-to-dry biomass ratio or NaOH loading (NaOH/DM) and the liquid-to-solid ratio (L/S). Optimization of these two parameters provided good results in terms of enzymatic hydrolysis at 5% (w w−1) solids loading, obtaining a total sugar concentration of 24.9 g L−1 and a total sugar production of 36.9 g 100 g−1 raw EW after pretreating the biomass at 20% NaOH/DM and L/S = 1/1. The second step of extrusion, when followed by a final washing step, provided a significant increase in glucose and xylose production when working at 10% NaOH/DM. For a soda loading of 20%, there was a clear improvement in sugars conversion yield after extrusion and washing: 71% for glucan conversion and 89% for xylan.

Non-Structural Carbohydrates Accumulation in Contrasting Rice Genotypes Subjected to High Night Temperatures

Non-structural carbohydrates (NSC) accumulation and photosynthesis traits were studied in two rice (Oryza sativa L.) genotypes maintained under control (22/30 °C - night/day) and at high night temperatures (HNT) (28/30 °C) conditions from heading to milk stage. Rice cultivars were Nagina22 - N22 and BRS Querência - Quer, which are tolerant and sensitive to high temperatures, respectively. The source-sink flow related attributes were tested to understand the nature of NSC accumulation and translocation. Compared to N22, Quer maintained higher stem starch in glucose on seventh day after heading and at milk stage independently of imposed temperatures. However, the levels of starch in glucose were lower for N22 meanwhile their total sugar concentration (TSC) were higher at control and at HNT at milk stage as compared to Quer. N22 maintained unaltered the spikelet sterility and 1000-grain weight across environments showing a consistent trend with its stem NSC translocation. Both genotypes showed similarity in some gas exchange and chlorophyll fluorescence performance suggesting unaffected photosystem II photochemistry, linear electron flux, and CO2 assimilation. Beyond indicating that source functioning was not the limiting factor for low TSC and starch in glucose levels found in N22 on seventh day after heading stage. Moreover, our data suggest that the higher translocation capacity shown by N22 can be involved in their lower spikelet sterility and 1000-grain weight stability across the environments. These results indicate that selecting genotypes with higher capacity to stem NSC translocation at HNT could lead to more grain yield stability in future climate scenarios.

PRODUKSI BIOETANOL DARI HIDROLISAT ASAM TEPUNG UBI KAYU DENGAN KULTUR CAMPURAN Trichoderma viride dan Saccharomyces cerevisiae (Ethanol Production From Acid Hydrolysate Cassava Flour with Mixed Culture Trichoderma viride and Saccharomyces cerevisiae)

The objective of this research was to produce bioethanol from acid hydrolysate cassava flour with mix cultured Trichoderma viride and Saccharomyces cerevisiae. The hydrolysis of cassava flour to glucose was conducted by 0.4 M sulfuric acid using autoclave at 121°C, pressure at 1 atm for 10 min. The fermentation were performed in batch systemfor 96 hours in 30°C. Mixed culture of T. viride and S. cerevisiae in the fermentation process of acid hydrolysate carried out in two methode that is gradually and simultaneously. The results showed the acid hydrolyzate of cassava flour has a total sugar concentration of 38.93 ± 8.09% (w/v) and reducing sugar concentration of 22.04 ± 4.31% (w/v) . In thebioethanol production process shows that the bioethanol concentration 6.77 ± 1.23% (v/v), yield 27,97% (v/w) and fermentation effciency 59,01% of the theoretical value was achieved using gradually addition of mixed culture, while simultaneously addition of mixed culture was produced ethanol concentration 4.96 ± 0.39%(v/v), yield 19.85% (v/w)and fermentation effciency 62.72% of the theoretical value.Keywords: Bioethanol, cassava flour, acid hidrolysate, Trichoderma viride, Saccharomyces cerevisiae ABSTRAKTujuan dari penelitian ini adalah untuk memproduksi bioetanol dari hidrolisat asam tepung ubi kayu dengan menggunakan kultur campuran Trichoderma viride and Saccharomyces cerevisiae. Hidrolisis tepung ubi kayu untuk menghasilkan glukosa dilakukan dengan menggunakan H2SO4 0.4M, pada suhu 121°C, tekanan 1 atm selama 10 menit. Prosesfermentasi dilaksanakan secara batch selama 96 jam pada suhu 30°C. Pencampuran kultur T. viride dan S. cerevisiae pada proses fermentasi hidrolisat asam dilakukan dalam dua metode yaitu secara bertahap dan secara simultan. Hasil penelitian menunjukkan hidrolisat asam tepung ubi kayu mempunyai konsentrasi total gula 38,93 ± 8,09% (b/v) dankonsentrasi gula reduksi 22,04 ± 4,31% (b/v). Pada proses produksi bioetanol menunjukan bahwa dengan pencampuran kultur secara bertahap menghasilkan konsentrasi bioetanol 6,77 ± 1,23% (v/v), rendemen 27,97% (v/w) dan efisiensi fermentasi 59,01% dari perolehan bioetanol secara teoritis, sedangkan dengan pencampuran kultur secara simultan menghasilkan konsentrasi bioetanol 4,96 ± 0,39%(v/v), rendemen 19,85% (v/w) dan efisiensi fermentasi 62,72% dariperolehan bioetanol secara teoritis.Kata kunci: Bioetanol, tepung ubi kayu, hidrolisat asam, Trichoderma viride, Saccharomyces cerevisiae

Separation of Xylose From Glucose Using Thin Film Composite (TFC) Nanofiltration Membrane: Effect of Pressure, Total Sugar Concentration and Xylose/Glucose Ratio

Xylose is an abundant raw material coexists with other sugars that can be turned into useful products, such as ethanol, xylitol and 2, 3-butanediol by microorganism such as yeasts, bacteria, and mycelial fungi. However, more than 80 % of the production cost of these products comes solely from the production of xylose. Presently, the separation of xylose from hemicellulose hydrolysate relies on chromatographic separation alone. The use of nanofiltration membrane may offer alternative in recovering xylose due to the differences in size compared to other sugars. The aim of this study is to evaluate the ability of membrane developed by interfacial polymerization reaction between triethanolamine (TEOA) (6 % w/v) and tri-mesoyl chloride (TMC) (0.15 % w/v) as monomers on polyethersulfone (PES) microporous substrate to separate xylose from glucose. In this study, factors affecting the process, namely pressure, concentration of total sugars in solution, and composition of monosaccharides in total sugar, were investigated using two-level factorial analysis. The experiment was performed using Amicon Milipore stirred cell (Model 8200) with constant stirring speed at 300 rpm and temperature at ambient. The glucose and xylose concentration was quantified using high performance liquid chromatography (HPLC). It is found that the developed nanofiltration membrane has the ability to separate xylose from glucose.The analysis of the experimental response revealed that the total sugar concentration and composition ratio of xylose: glucose had significant interactive effect on xylose separation factor. Overall from the present study, it can be concluded that nanofiltration has high potential to replace currently in use chromatographic method in xylose separation.

Optimization of Two-Step Acid-Catalyzed Hydrolysis of Oil Palm Empty Fruit Bunch for High Sugar Concentration in Hydrolysate

Getting high sugar concentrations in lignocellulosic biomass hydrolysate with reasonable yields of sugars is commercially attractive but very challenging. Two-step acid-catalyzed hydrolysis of oil palm empty fruit bunch (EFB) was conducted to get high sugar concentrations in the hydrolysate. The biphasic kinetic model was used to guide the optimization of the first step dilute acid-catalyzed hydrolysis of EFB. A total sugar concentration of 83.0 g/L with a xylose concentration of 69.5 g/L and a xylose yield of 84.0% was experimentally achieved, which is in well agreement with the model predictions under optimal conditions (3% H2SO4and 1.2% H3PO4, w/v, liquid to solid ratio 3 mL/g, 130°C, and 36 min). To further increase total sugar and xylose concentrations in hydrolysate, a second step hydrolysis was performed by adding fresh EFB to the hydrolysate at 130°C for 30 min, giving a total sugar concentration of 114.4 g/L with a xylose concentration of 93.5 g/L and a xylose yield of 56.5%. To the best of our knowledge, the total sugar and xylose concentrations are the highest among those ever reported for acid-catalyzed hydrolysis of lignocellulose.