Extraction of Eucommia ulmoides gum and microbial lipid from Eucommia ulmoides Oliver leaves by dilute acid hydrolysis.

OBJECTIVES: Eucommia ulmoides gum (EUG) is an important natural biomass rubber material, which is usually extracted from Eucommia ulmoides Oliver (EUO). In the extraction process of EUG, pretreatment is the most important step which can efficiently damage EUG-containing cell wall and improve yield of EUG. RESULTS: The FT-IR, XRD, DSC and TG results showed that the thermal properties and structure of the EUG from the dilute acids hydrolysis residue are similar with that of the EUG directly extracted from EUO leaves (EUGD). EUO leaves hydrolysis with AA had the highest EUG yield (16.1%), which was higher than the EUGD yield (9.5%). In the case of the EUO leaves hydrolysis with 0.33 ~ 0.67 wt% of acetic acid (AA), the total sugar was stable in the range of 26.82-27.67 g/L. Furthermore, the EUO leaves acid hydrolysate (AA as reagent) was used as carbon sources for lipid-producing fermentation by Rhodosporidium toruloides. After 120 h of fermentation, the biomass, lipid content and lipid yield were 12.13 g/L, 30.16% and 3.64 g/L, respectively. The fermentation results indicated organic acids were no toxic for Rhodosporidium toruloides and the AA also could be used as carbon source for fermentation.

Ultrasonic­assisted molten salt hydrates pretreated Eucheuma cottonii residues as a greener precursor for third-generation l-lactic acid production.

This study aims to establish an efficient pretreatment method that facilitates the conversion of sugars from macroalgae wastes, Eucheuma cottonii residues (ECRs) during hydrolysis and subsequently enhances l-lactic acid (L-LA) production. Hence, ultrasonic-assisted molten salt hydrates (UMSHs) pretreatment was proposed to enhance the accessibility of ECRs to hydrolyze into glucose through dilute acid hydrolysis (DAH). The obtained hydrolysates were employed as the substrate in producing L-LA by separate hydrolysis and fermentation (SHF). The maximum glucose yield (97.75 %) was achieved using UMSHs pretreated ECRs with 40 wt% ZnCl2 at 80 °C for 2 h and followed with DAH. The optimum glucose to L-LA yield obtained for SHF was 90.08 % using 5 % (w/w) inoculum cell densities of B. coagulans ATCC 7050 with yeast extract (YE). A comparable performance (89.65 %) was obtained using a nutrient combination (lipid-extracted Chlorella vulgaris residues (CVRs), vitamin B3, and vitamin B5) as a partial alternative for YE.

Re-examination of dilute acid hydrolysis of lignocellulose for production of cellulosic ethanol after de-bottlenecking the inhibitor barrier.

Dilute acid hydrolysis of lignocellulose biomass had been used for production of cellulosic ethanol since 1940 s. The major technical barrier is the acid catalyzed dehydration of monosaccharides to furan aldehydes (furfural and 5-hydroxymethylfurfural), resulting in the high loss of fermentable sugars and significant inhibition on the fermentability of ethanologenic strains. This study re-examined the dilute acid hydrolysis of corn stover and cellulosic ethanol fermentation after a novel biodetoxification approach was introduced to de-bottleneck the inhibitor barrier. The cocktail of sulfuric acid, phosphoric acid and oxalic acid hydrolyzed corn stover to the 51.1 g/L of glucose (0.50 g/g cellulose) and 18.1 g/L of xylose (0.22 g/g xylan). The furfural, 5-hydroxymethylfurfural and acetic acid in the corn stover hydrolysate were completely removed by Paecilomyces variotii FN89, leading to the successful ethanol fermentation of 24.2 g/L, corresponding to 72.6 kg per metric ton of dry corn stover. No wastewater streams, solid wastes and toxic compounds were generated in hydrolysis, biodetoxification and fermentation. The techno-economic evaluations suggest that the cost reduction of replacing cellulase enzyme with cheap acid catalysts compensated the partial ethanol loss of sugar conversion to inhibitors (21.5-89.1%). The re-examination of acid hydrolysis process reveals that a substantial breakthrough in highly active and selective acid catalyst is required for acid hydrolysis to compete with enzymic hydrolysis for cellulosic ethanol fermentation.

Ultrasound-assisted dilute acid hydrolysis for production of essential oils, pectin and bacterial cellulose via a citrus processing waste biorefinery.

An orange peel waste biorefinery was developed employing a design of experiments approach to optimize the ultrasound-assisted dilute acid hydrolysis process applied for production of useful commodities. Central composite design-based response surface methodology was used to approximate the combined effects of process parameters in simultaneous production of essential oils, pectin and a sugar-rich hydrolyzate. Application of a desirability function determined the optimal conditions required for maximal production efficiency of essential oils, pectin and sugars as 5.75% solid loading, 1.21% acid concentration and 34.2 min duration. Maximum production yields of 0.12% w/w essential oils, 45% w/w pectin and 40% w/w sugars were achieved under optimized conditions in lab- and pilot-scale facilities. The hydrolyzate formed was applied in bacterial cellulose fermentations producing 5.82 g biopolymer per 100 g waste. Design of experiments was efficient for process analysis and optimization providing a systems platform for the study of biomass-based biorefineries.

Acetone, butanol, and ethanol production from puerariae slag hydrolysate through ultrasound-assisted dilute acid by Clostridium beijerinckii YBS3.

In this study, puerariae slag (PS) was evaluated as a renewable raw material for acetone-butanol-ethanol (ABE) fermentation. To accelerate the hydrolysis of PS, the method of ultrasound-assisted dilute acid hydrolysis (UAAH) was used. With this effort, 0.69 g reducing sugar was obtained from 1 g raw material under the optimal pretreatment condition. Subsequently, the butanol and total solvent production of 8.79 ± 0.16 g/L and 12.32 ± 0.26 g/L were obtained from the non-detoxified diluted hydrolysate, and the yield and productivity of butanol were 0.19 g/g and 0.12 g/L/h, respectively. Additionally, the changes in the structure of PS after different pretreatment methods were observed using SEM and FT-IR. UAAH resulted in more severe and distinct damage to the dense structure of PS. This study suggests that the UAAH is an attainable but effective pretreatment method, thereby is a promising technique for lignocellulose hydrolysis and improve butanol production.

Production of xylose enriched hydrolysate from bioenergy sorghum and its conversion to ß-carotene using an engineered Saccharomyces cerevisiae.

A new bioprocess has been developed that allows for producing ß-carotene from the xylose portion of bioenergy sorghum. Bioenergy sorghum was pretreated in a pilot-scale continuous hydrothermal reactor followed by disc refining. Xylose was extracted using low-severity dilute acid hydrolysis. A xylose yield of 64.9% (17.4 g/L) was obtained by hydrolyzing at 120 °C for 5 min with 2% sulfuric acid. The xylose-enriched syrup was separated and concentrated to either 32 g xylose/L (medium-concentrated hydrolysate, MCB) or 66 g xylose/L (high-concentrated hydrolysate, HCB). The non- (NCB), medium-, and high-concentrated xylose syrup were neutralized and fermented to ß-carotene using Saccharomyces cerevisiae strain SR8B, which had been engineered for xylose utilization and ß-carotene production. In HCB, MCB, and NCB cultures, the yeast produced ß-carotene titers of 114.50 mg/L, 93.56 mg/L, and 82.50 mg/L, which corresponds to specific yeast biomass productions of 7.32 mg/g DCW, 8.10 mg/g DCW, and 8.29 mg/g DCW, respectively.

Intensification of dilute acid hydrolysis of spent tea powder using ultrasound for enhanced production of reducing sugars.

Spent tea (ST) powder is one of the potential sustainable sources available abundantly and can be utilized to produce reducing sugars required for production of platform chemicals. The current study aims at intensifying the reducing sugars production based on ultrasound assisted dilute acid hydrolysis (UADAH). The effects of reaction time, solid liquid ratio, acid concentration and temperature on the yield of reducing sugars were investigated initially for UADAH process based on ultrasonic (US) horn. The highest yield of 24.75 g/L for the reducing sugars was obtained at solid liquid ratio of 1:8, acid concentration of 1% w/v and temperature of 60 °C within 120 min. Use of oxidants like hydrogen peroxide (H2O2) and Fenton's reagent to further intensify the production has also been studied. Use of H2O2 at optimum loading of 0.75 g/L resulted in reducing sugars yield of 26.2 g/L within 75 min while using same H2O2 loading with FeSO4 at loading of 0.75 g/L along with UADAH reduced the reaction time to 60 min for almost similar yield. Large scale studies performed using US flow cell revealed that yield of reducing sugars as 22.4 g/L is obtained in 120 min in the case of only UADAH, while in the case of UADAH along with H2O2 and Fenton's reagent, similar yield of reducing sugars was obtained in only 90 and 60 min respectively. UADAH in combination with oxidants has been demonstrated as an effective and intensified approach to produce reducing sugars from spent tea powder available as sustainable source.

Valorization of food-waste hydrolysate by Lentibacillus salarius NS12IITR for the production of branched chain fatty acid enriched lipid with potential application as a feedstock for improved biodiesel.

Oxidation stability and cold flow properties of biodiesel can be improved by using lipid with enriched branched-chain fatty acid (BCFA) as a feedstock. A halophilic bacterium was utilized for the production of BCFA enriched lipid from acid hydrolysate of food-waste. The maximum reducing sugar obtained by hydrolysis of wheat bran, rice bran, mango peel, and orange peel were 64.52 ±â€¯0.57, 38.7 ±â€¯0.58, 55.64 ±â€¯1.14, 36.29 ±â€¯0.54 g/L, respectively. On assessing these hydrolysates as feedstock for growth of halophilic bacterium Lentibacillus salarius NS12IITR at 10 g/L reducing sugar concentration, wheat bran hydrolysate was found to be best in-terms of sugar consumption (92%), lipid production (0.70 ±â€¯0.029 g/L) and maximum branched-chain fatty acid methyl ester (FAME) (81 ±â€¯4.72% of total FAME). At 20 g/L of reducing sugar concentration of wheat bran hydrolysate, the biomass and lipid yields were almost doubled. Efficient lipid extraction from cell, involving thermolysis at 85 °C and pH 2 along with osmotic shock resulted in isolation of 69% of total lipid.

Optimization of hydrothermal conversion of bamboo (Phyllostachys aureosulcata) to levulinic acid via response surface methodology.

In this study, the dilute acid hydrolysis of lignocellulosic bamboo (Phyllostachys aureosulcata) particles to levulinic acid in a hydrothermal synthesis reactor is reported. The aim of the study was to optimize the reaction conditions for maximum levulinic acid production in terms of reaction time (t), reaction temperature (T) and HCl concentration (cHCl) via Response Surface Methodology (RSM). A maximum levulinic acid yield of 9.46 w% was predicted at the following reaction conditions: t of 3 h, T of 160 °C and cHCl of 0.37 M. A maximal experimental yield of levulinic acid of 10.13 w% was observed, which in respect to the cellulose fraction of the bamboo particles corresponds to 34.60 w% or 48.05 mol%. Furfural, which is formed by the hemicellulose fraction of bamboo, has not been observed within the boundaries of the RSM model, since it is already degraded under the given reaction conditions. The conversion of levulinic acid and furfural occurred more or less simultaneously, however, furfural was more vulnerable to degradation reactions at the given process conditions. Therefore, if both fractions (cellulose + hemicellulose) are required to be valorized, further optimization is required. However, the global results of this study provide insight in the potential of lignocellulosic bamboo as an alternative platform to fossil sources.

Kinetic and thermodynamic analysis of dilute acid hydrolysis of sugarcane bagasse.

This study has investigated kinetic and thermodynamic features of dilute acid (2% v/v H2SO4, 1:30 w/v) hydrolysis of sugarcane bagasse. Time profiles of xylose formation in range of 100°-130 °C and treatment period of 0-120 min have been analysed with modified biphasic Saeman model. Generation of glucose, arabinose and inhibitory products (furfural, 5-HMF and acetic acid) have also been analysed. Easy-to-hydrolyse fraction of hemicellulose increased with temperature. Activation energies for hydrolysis and xylose degradation were 60.3 and 83.4 kJ/mol, respectively. Although maximum xylose yield (0.81 g/g hemicellulose) was obtained at 130 °C, significant fraction of xylose was converted to inhibitory products. Thermodynamic analysis revealed ΔH = 57.06 kJ/mol and ΔS = -1.05 kJ/mol for hydrolysis. Moreover, xylose formation is thermodynamically more favoured (ΔG = 468.53 kJ/mol) than degradation (ΔG = 482.17 kJ/mol). Optimum conditions for hydrolysis are: temperature = 120 °C, time = 30 min, xylose yield = 0.76 g/g hemicellulose.

Insight into the evolution of the proton concentration during autohydrolysis and dilute-acid hydrolysis of hemicellulose.

BACKGROUND: During pretreatment, hemicellulose is removed from biomass via proton-catalyzed hydrolysis to produce soluble poly- and mono-saccharides. Many kinetic models have been proposed but the dependence of rate on proton concentration is not well-defined; autohydrolysis and dilute-acid hydrolysis models apply very different treatments despite having similar chemistries. In this work, evolution of proton concentration is examined during both autohydrolysis and dilute-acid hydrolysis of hemicellulose from green bamboo. An approximate mathematical model, or "toy model", to describe proton concentration based upon conservation of mass and charge during deacetylation and ash neutralization coupled with a number of competing equilibria, was derived. The model was qualitatively compared to experiments where pH was measured as a function of time, temperature, and initial acid level. Proton evolution was also examined at room temperature to decouple the effect of ash neutralization from deacetylation. RESULTS: The toy model predicts the existence of a steady-state proton concentration dictated by equilibrium constants, initial acetyl groups, and initial added acid. At room temperature, it was found that pH remains essentially constant both at low initial pH and autohydrolysis conditions. Acid is likely in excess of the neutralization potential of the ash, in the former case, and the kinetics of neutralization become exceedingly small in the latter case due to the low proton concentration. Finally, when the hydrolysis reaction proceeded at elevated temperatures, one case of non-monotonic behavior in which the pH initially increased, and then decreased at longer times, was found. This is likely due to the difference in rates between neutralization and deacetylation. CONCLUSIONS: The model and experimental work demonstrate that the evolution of proton concentration during hydrolysis follows complex behavior that depends upon the acetyl group and ash content of biomass, initial acid levels and temperature. In the limit of excess added acid, pH varies very weakly with time. Below this limit, complex schemes are found primarily related to the selectivity of deacetylation in comparison to neutralization. These findings indicate that a more rigorous approach to models of hemicellulose hydrolysis is needed. Improved models will lead to more efficient acid utilization and facilitate process scale-up.

Screening of Yeasts for Selection of Potential Strains and Their Utilization for In Situ Microbial Detoxification (ISMD) of Sugarcane Bagasse Hemicellulosic Hydrolysate.

Many toxic compounds are produced and released in the hemicellulosic hydrolyzates during the acid pretreatment step, which are required for the disruption of the lignocelluloses matrix and sugars release. The conventional methods of detoxification i.e. overliming, activated charcoal, ion exchange or even membrane-based separations have the limitations in removal of these toxic inhibitors in fermentation process. Hence, it is imperative to explore biological methods to overcome the inhibitors by minimizing the filtration steps, sugar loss and chemical additions. In the present study we screened sixty-four strains of yeasts to select potential strains for detoxification of furfural, acetic acid, ferulic acid, 5-hydroxymethyl furfural (5-HMF) as carbon and energy source. Among these strains Pichia occidentalis M1, Y1'a, Y1'b and Y3' showed a significant decrease in the toxic compounds but we selected two best yeast strains i.e. P. occidentalis Y1'a and P. occidentalis M1 for the further experiments with an aim to remove the fermentation inhibitors. The yeasts P. occidentalis Y1'a and P. occidentalis M1 were grown aerobically in sugarcane bagasse hemicellulose hydrolysate under submerged cultivation. For each yeast, a 2(2) full factorial design was performed considering the variables-pH (4.0 or 5.0) and agitation rate (100 or 300 rpm), and the percentage removal of HMF, furfural, acetic acid and phenols from hemicellulosic hydrolysates were responsive variables. After 96 h of biological treatment, P. occidentalis M1 and P. occidentalis Y1'a showed 42.89 and 46.04 % cumulative removal of inhibitors, respectively.

Optimization of High Solids Dilute Acid Hydrolysis of Spent Coffee Ground at Mild Temperature for Enzymatic Saccharification and Microbial Oil Fermentation.

Soluble coffee, being one of the world's most popular consuming drinks, produces a considerable amount of spent coffee ground (SCG) along with its production. The SCG could function as a potential lignocellulosic feedstock for production of bioproducts. The objective of this study is to investigate the possible optimal condition of dilute acid hydrolysis (DAH) at high solids and mild temperature condition to release the reducing sugars from SCG. The optimal condition was found to be 5.3 % (w/w) sulfuric acid concentration and 118 min reaction time. Under the optimal condition, the mean yield of reducing sugars from enzymatic saccharification of defatted SCG acid hydrolysate was 563 mg/g. The SCG hydrolysate was then successfully applied to culture Lipomyces starkeyi for microbial oil fermentation without showing any inhibition. The results suggested that dilute acid hydrolysis followed by enzymatic saccharification has the great potential to convert SCG carbohydrates to reducing sugars. This study is useful for the further developing of biorefinery using SCG as feedstock at a large scale.

Enhanced biohydrogen and subsequent biomethane production from sugarcane bagasse using nano-titanium dioxide pretreatment.

Nano-titanium dioxide (nanoTiO2) under ultraviolet irradiation (UV) followed by dilute sulfuric acid hydrolysis of sugarcane bagasse was used to enhance the production of biohydrogen and biomethane in a consecutive dark fermentation and anaerobic digestion. Different concentrations of 0.001, 0.01, 0.1 and 1g nanoTiO2/L under different UV times of 30, 60, 90 and 120min were used. Sulfuric acid (2%v/v) at 121°C was used for 15, 30 and 60min to hydrolyze the pretreated bagasse. For acidic hydrolysis times of 15, 30 and 60min, the highest total free sugar values were enhanced by 260%, 107%, and 189%, respectively, compared to samples without nanoTiO2 pretreatment. The highest hydrogen production samples for the same acidic hydrolysis times showed 88%, 127%, and 25% enhancement. The maximum hydrogen production of 101.5ml/g VS (volatile solids) was obtained at 1g nanoTiO2/L and 120min UV irradiation followed by 30min acid hydrolysis.

Obtaining fermentable sugars by dilute acid hydrolysis of hemicellulose and fast pyrolysis of cellulose.

The objective of this study was to get fermentable sugars by dilute acid hydrolysis of hemicellulose and fast pyrolysis of cellulose from sugarcane bagasse. Hemicellulose could be easily hydrolyzed by dilute acid as sugars. The remained solid residue of acid hydrolysis was utilized to get levoglucosan by fast pyrolysis economically. Levoglucosan yield from crystalline cellulose could be as high as 61.47%. Dilute acid hydrolysis was also a promising pretreatment for levoglucosan production from lignocellulose. The dilute acid pretreated sugarcane bagasse resulted in higher levoglucosan yield (40.50%) in fast pyrolysis by micropyrolyzer, which was more effective than water washed (29.10%) and un-pretreated (12.84%). It was mainly ascribed to the effective removal of alkali and alkaline earth metals and the accumulation of crystalline cellulose. This strategy seems a promising route to achieve inexpensive fermentable sugars from lignocellulose for biorefinery.

Hemicellulosic ethanol production by immobilized cells of Scheffersomyces stipitis: effect of cell concentration and stirring.

Bioconversion of hemicellulosic hydrolysate into ethanol plays a pivotal role in the overall success of biorefineries. For the efficient fermentative conversion of hemicellulosic hydrolysates into ethanol, the use of immobilized cells system could provide the enhanced ethanol productivities with significant time savings. Here, we investigated the effect of 2 important factors (e.g., cell concentration and stirring) on ethanol production from sugarcane bagasse hydrolysate using the yeast Scheffersomyces stipitis immobilized in calcium alginate matrix. A 2(2) full factorial design of experiment was performed considering the process variables- immobilized cell concentration (3.0, 6.5 and 10.0 g/L) and stirring (100, 200 and 300 rpm). Statistical analysis showed that stirring has the major influence on ethanol production. Maximum ethanol production (8.90 g/l) with ethanol yield (Yp/s) of 0.33 g/g and ethanol productivity (Qp) of 0.185 g/l/h was obtained under the optimized process conditions (10.0 g/L of cells and 100 rpm).