Thermal Acid Hydrolysis Research Articles

Thermal acid hydrolysis modulates the solubility of quinoa protein: The formation of different types of protein aggregates

The poor solubility of plant-based proteins is the main factor limiting their utilization. In this study, how thermal acid hydrolysis (0, 0.05, 0.1, 0.2 and 0.5 M HCl; 90 °C) changed the solubility of quinoa proteins was investigated by monitoring the changes of the degree of hydrolysis (DH), sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) profiles, particle size, zeta-potential, surface hydrophobicity, intrinsic fluorescence and transmission electron microscopy (TEM) morphology with different hydrolysis time. We found that 11 S globulins and 2 S albumins were the major components of differently-sized quinoa protein particles (i.e., small/soluble or large/precipitated particles), which were the main form of quinoa proteins existing in water solution. Compared to precipitated fractions, 7 S globulins were more abundant in the soluble fractions of quinoa proteins. The solubility of quinoa proteins was determined by the combined effect of protein-protein interactions and acid hydrolysis, which was highly related to acid concentration. At 0 M HCl, heat-induced aggregation caused the decreased solubility because of the decreased electrostatic repulsion and hydrophobic interactions among quinoa protein molecules. At 0.05 and 0.1 M HCl, the solubility was also dominated by heat-induced protein aggregation without changes over 0.5–8 h treatment. At 0.2 M HCl, the solubility and the DH increased with hydrolysis time due to the formation of long and fibrillar protein aggregates. At 0.5 M HCl, strong acid hydrolysis greatly improved the solubility of quinoa proteins, forming short and worm-like strands and subsequently assembling into larger aggregates. This study would promote the utilization of quinoa proteins as an alternative protein.

Bioethanol Production from Marine Macroalgae Waste: Optimisation of Thermal acid Hydrolysis

Marine macroalgae waste, resulting from the accumulation of drifted algal biomass along the coastline, might be a relevant complementary raw material aiming sustainable bioethanol production. In the present study, the optimisation of thermal acid hydrolysis was performed using response surface methodology (RSM) considering the effect of three variables, namely, reaction time (10–60 min), acid concentration (0.1–2.5% (v/v) H2SO4) and biomass:acid ratio (5–15% (w/v)) on sugar concentration and yield. Under the best conditions, the resulting hydrolysates were fermented (7 days, 30 °C, 150 rpm, commercial yeast) to produce bioethanol. A statistically valid second-order model was obtained (r2 = 0.9876; Prob > F lower than 0.05), showing that sugar concentration is mostly influenced by the biomass:acid ratio while reaction time was not significant. The maximum predicted sugar concentration was 18.4 g/L, being obtained at 2.5% H2SO4 concentration and 15% (w/v) biomass:acid ratio, corresponding to a sugars yield of 12.5 g/100 g (less 36% than that obtained using 10% (w/v)). At the best conditions, the hydrolysates were fermented to obtain a bioethanol concentration up to 2.4 g/L and a 21 mgbioethanol/gbiomass yield, emphasizing the biomass potential for bioenergy production.Graphical

Optimization, Scale-Up, and Economic Analysis of the Ethanol Production Process Using Sargassum horneri

Recently, the extensive spread of some algae along coastlines has surged into unmanageable thick decomposition layers. This study aimed to demonstrate the use of Sargassum horneri as a biomass resource for ethanol production through the continuous hydrolysis, enzymatic saccharification, and fermentation process. Sugars from S. horneri were obtained using a combination of thermal acid hydrolysis and enzymatic saccharification. The optimal conditions for thermal acid hydrolysis involved a 10% (w/v) S. horneri slurry treated with 100 mM H2SO4 at 121 °C for 60 min; enzymatic saccharification using 16 U/mL Cellic CTec2 further boosted the monosaccharide concentration to 23.53 g/L. Fermentation experiments were conducted with mannitol-adapted Saccharomyces cerevisiae BY4741 using S. horneri hydrolysate. Enhanced ethanol production was observed in the hydrolysate, particularly with mannitol-adapted S. cerevisiae BY4741, which yielded 10.06 g/L ethanol. Non-adapted S. cerevisiae produced 8.12 g/L ethanol, as it primarily utilized glucose and not mannitol. Regarding ethanol fermentation using 5 L- and 500 L-scale fermenters, the ethanol concentrations reached 10.56 g/L and 7.88 g/L with yields of 0.51 and 0.45, respectively, at 48 h. This study confirmed the economic viability of ethanol production using waste seaweed with optimized pretreatment conditions and the adaptive evolution of S. cerevisiae to mannitol.

Microalgae to Bioenergy: Optimization of Aurantiochytrium sp. Saccharification.

Microalgae are a promising feedstock for bioethanol production, essentially due to their high growth rates and absence of lignin. Hydrolysis-where the monosaccharides are released for further fermentation-is considered a critical step, and its optimization is advised for each raw material. The present study focuses on the thermal acid hydrolysis (with sulfuric acid) of Aurantiochytrium sp. through a response surface methodology (RSM), studying the effect of acid concentration, hydrolysis time and biomass/acid ratio on both sugar concentration of the hydrolysate and biomass conversion yield. Preliminary studies allowed to establish the range of the variables to be optimized. The obtained models predicted a maximum sugar concentration (18.05 g/L; R2 = 0.990) after 90 min of hydrolysis, using 15% (w/v) biomass/acid ratio and sulfuric acid at 3.5% (v/v), whereas the maximum conversion yield (12.86 g/100 g; R2 = 0.876) was obtained using 9.3% (w/v) biomass/acid ratio, maintaining the other parameters. Model outputs indicate that the biomass/acid ratio and time are the most influential parameters on the sugar concentration and yield models, respectively. The study allowed to obtain a predictive model that is very well adjusted to the experimental data to find the best saccharification conditions for the Aurantiochytrium sp. microalgae.

Enhancement of galactose uptake for bioethanol production from Eucheuma denticulatum hydrolysate using galactose-adapted yeasts.

Eucheuma denticulatum is a red macroalgae with a high carbohydrate content. The fermentable sugars from E. denticulatum were obtained through sequential thermal acid hydrolysis, enzymatic saccharification, and detoxification. Thermal acid hydrolysis of E. denticulatum was optimized under the condition of 10% (w/v) slurry content and 300mM HNO3 at 121℃ for 90min. The maximum monosaccharide concentration after thermal acid hydrolysis was 31.0g/L with an efficiency (ETAH) of 44.7%. By further enzymatic hydrolysis of pretreated biomass solution under 20 U/mL Cellic CTec2 at 50℃ and 160rpm for 72h, the maximum monosaccharide concentration reached 79.9g/L with an efficiency of 66.2% (ES). To remove 5-hydroxymethylfurfural (5-HMF), a fermentation inhibitor, absorption using 2% activated carbon was performed for 2min. Ethanol fermentation was performed using wild-type and high galactose-adapted strains of Saccharomyces cerevisiae, Kluyveromyces marxianus, and Candida lusitaniae. As a result, galactose-adapted strains showed higher ethanol production than wild-type strains. Especially, the fermentation result by adaptively evolved S. cerevisiae produced the highest ethanol of 37.6g/L and with YEtOH of 0.48g/g. Moreover, the transcript level of MIG1 in the galactose-adapted strain was slightly lower than that in the wild-type strain. The application of adaptive evolution of microorganisms was efficient for bioethanol production.

Modification of bioethanol production in an innovative pneumatic digester with non-thermal cold plasma detoxification

An anaerobic pneu-mechanical digester (PD) was designed to ferment lignocellulosic compounds. So, wheat and rice straws were pretreated using an ultrasound-acid, and then thermal-acid hydrolysis was conducted. Hydrolysis optimization was performed using the response surface method and the optimal points for time, temperature, and acid concentration were 45 min, 148.4 °C, and 2.04 % v/v, respectively. Cold plasma was then used as detoxification to reduce the amount of inhibitory compounds and acids. This method was capable of reducing the amounts of acetic acid, formic acid and furfural by 73, 83 and 68 % in hydrolyzed biomass, respectively. The biomass was fermented in a PD for 20 days and compared with a conventional digester (CD). The obtained results showed that the PD could increase the efficiency of bioethanol by 37 % in the detoxified state and 22 % in the non-detoxified state after 20 days of fermentation compared to the CD. Moreover, H2S, CO and O2 were measured during fermentation process. In PD, the amount of H2S and O2 was lower than CD, but CO was significantly higher in the PD.

Effect of cold plasma on breaking activated sludge and the output dominance of protein

ABSTRACT Upon contacting with water, cold plasma should produce numerous ozone molecules and free electrons at room temperature. In this study, a cold plasma generator was used to break the walls of residual activated sludge obtained from domestic sewage. The impact was mainly influenced by the ozone generated. With 800 W power, sludge wastewater pH of 12.0, and under continuous treatment for 10 h, the system’s reduction efficiency for the dry sludge was ≈90%. Furthermore, the organic matter content (especially protein) of the upper layer of the sludge solution increased a lot after the sludge digestion. This observation proved the reduction of sludge from both sides. Moreover, when the cold plasma technique was compared with thermal acid hydrolysis, thermal alkali hydrolysis, and ultrasonication for extracting protein from activated sludge, cold plasma wall-breaking sludge exhibited the highest efficiency, reaching 38.2% under ambient temperature. After the analysis, the toxic metal content in the extracted protein was near zero, which is a level other protein extraction methods via sludge breaking have not achieved to date, we attribute this efficiency to free electrons the cold plasma produce. These species promote the transformation of metal ions into atomic metals, thereby facilitating their removal.

The combined effect of thermal-acid hydrolysis, periodate oxidation, and iodine species removal on the properties of native tapioca (Manihot esculenta Crantz) starch

Through a four-step top-down approach, native tapioca starch (NTS) was thermally acid-hydrolyzed, periodate-oxidized with subsequent removal of iodine species (i.e., IO4(−), IO3(−), I(−), and I2), and dialdehyde tapioca starch (DTS) alcohol-precipitation. The percent yield was ∼91%. Analyses confirmed the presence of aldehydic functionalities (∼71%), effectual iodine species removal (∼98%), and enhanced water-solubility (∼96.57%). Besides, the combined treatment significantly reduced the Mw (∼57.81 kDa) and ameliorated homogeneity as well as thermal stability (Tmax ∼ 667.15 °C). Structural-spectral characterization also confirmed the presence of aldehydic functionality, polymorphic transition (C- to A-type), and a higher degree of crystallinity (∼91.77%), the latter further corroborated by thermal analysis. The morphological study revealed that the combined treatment reduced size (∼393.55-nm-diameter and ∼5.22-μm-length) and changed shape into rod-like crystals. DTS showed considerably and significantly low cytotoxicity to HaCaT cells in vitro at the concentrations assayed over the test period (24 h). DTS's conformation was most stable at −289 kcal/mol and −151.7 au heat formation and minimum potential energies, respectively. Overall, these results demonstrated that the combined treatment had no deleterious effects on NTS's properties, thus yielded DTS with ideal properties for multifarious uses.

Anaerobic biohydrogen production from biodetoxified rice straw hydrolysate

Thermal acid hydrolysis is the most common pretreatment method used to deal with waste lignocellulosic biomass. However, furan derivatives (5‑hydroxy-methylfurfural (5-HMF) and furfural) are unavoidably produced and influence downstream biofuel production. Biological methods are superior to physical and chemical methods in detoxifying 5-HMF and furfural because of economic concerns. Integrating the biodetoxification process into the lignocellulose pretreatment and downstream biofuel production procedure is an important issue. The previous novel strain Burkholderia cepacia H-2 capable of quickly degrading 5-HMF and furfural was applied in the biodetoxification process. In this study, the acid sorts and concentration effects on thermal acid rice straw hydrolysis were investigated first. Rice straw hydrolysates with various dilution ratios were then biodetoxified using on-site inoculating novel strain B. cepacia H-2. The biodetoxified rice straw hydrolysate was then used for biohydrogen production using dark fermentation. The highest hydrolysis efficiency and reducing sugar were 49% and 15.6 g/L, respectively when applying 0.5 M HCl to deal with 5% rice straw at 121°C for 15 min. The 5-HMF and furfural in the 2-fold diluted rice straw hydrolysate could be completely biodetoxified within 12 hrs. The hydrolysate hydrogen yields with and without biodetoxification were 0.90 and 0.64 mmol H2/mmol sugar, respectively. The biodetoxification process using the novel strain B. cepacia H-2 was successfully established and could be integrated into the lignocellulose pretreatment and downstream biofuel production procedure as using the rice straw as the feedstock.

Enhancement of catabolite regulatory genes in Saccharomyces cerevisiae to increase ethanol production using hydrolysate from red seaweed Gloiopeltis furcata

Glucose and galactose are monosaccharides obtained from Gloiopeltis furcata (Red algae). A total monosaccharide yield of 62.3 g/L was obtained from G. furcata using thermal acid hydrolysis and enzymatic saccharification. Activated carbon was used to eliminate hydroxymethylfurfural (HMF) from the hydrolysate. Previously obtained monosaccharides are used for ethanol production by Saccharomyces cerevisiae. S. cerevisiae consumes glucose first, then galactose. The methods for reducing fermentation time and increasing the ethanol yield coefficient using the simultaneous consumption of glucose and galactose have been evaluated. Gal3p and Gal80p of S. cerevisiae act as signal transducers that govern the galactose inducer Gal4p mediated transcriptional activation of the Gal gene family. Gal80p binds to Gal4p for transcription deactivation. Therefore, Gal80p was deleted for Gal4p expression without interruption.

Evaluation of seasonal variation and the optimization of reducing sugar extraction from Ulva prolifera biomass using thermochemical method

Green macroalgae comprise significant amount of structural carbohydrates for their conversion to liquid biofuels. However, it generally relies on species characteristics and the variability in seasonal profile to determine its route for bioprocessing. Hence, this study was conducted to analyze the indigenous marine macroalgal strain (Ulva prolifera) with respect to periodic trend and reducing sugar extraction. Consequently, in our investigation, the monthly variation in sugar profile and bioethanol yield was assessed between the monsoon and post-monsoon seasons, of which relatively high reducing sugar and fermentative bioethanol yield of about 0.152 ± 0.009 g/gdw and 6.275 ± 0.161 g/L was obtained for the October-month isolate (MITM10). Thereafter, the biochemical profile of this collected biomass (MITM10) revealed carbohydrate 34.98 ± 3.30%, protein 12.45 ± 0.49%, and lipid 1.93 ± 0.07%, respectively, on dry weight basis. Of these, the total carbohydrate fraction yielded the maximum reducing sugar of 0.156 ± 0.005 g/gdw under optimal conditions (11.07% (w/v) dosage, 0.9 M H2SO4, 121°C for 50 min) for thermal-acid hydrolysis. Furthermore, the elimination of polysaccharides was confirmed using the characterization techniques scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Therefore, the present thermochemical treatment method provides a species-specific novel strategy to breakdown the macroalgal cell wall polysaccharides that enhances sugar extraction for its utilization as an efficient bioenergy resource.

Development and validation of stability indicating method for determination of sodium citrate in pediatric cough syrup

Sodium Citrate is widely used in analytical and food processes. It is used in various medical applications as anticoagulant in blood transfusion process and bladder washout. It is used in cough preparation as mucolytic. There are many methods for determination of Sodium Citrate in different preparations. Some of which use spectrophotometric methods, others used HPLC methods. The USP method uses titration and determining the end point potentionometrically. Many arguments take place between the Drug Regulatory Affairs and manufacturers regarding the appearance of the colour at the end point. The objective of this study is to develop and validate a simple, easy and precise HPLC stability indicating method for routine work and to be submitted to the Drug Regulatory Affairs. Chromatographic system with detector PDA at 210nm is utilized, Reprosil-XR C18, 250 mm×4 mm, 5 µm column is used. Column temperature 300C and flow rate of 1 ml/min. A clear peak of acceptable purity at 3.38 min retention time appears. The method is subjected to thermal stress, acid and base hydrolysis at extreme pH and forced oxidation. The result is that there is no interference of degradation products with the substance peak. The method is then subjected to validation study according to the ICH guidelines. The method comply the specificity, precision, linearity, accuracy and robustness acceptable criteria. Thus, the method satisfies the stability indicating method and validation requirements that it can be submitted to the Drug Regulatory Affairs and used in QC routine activities and stability studies.

Enhancement of Galactose Uptake from Kappaphycus alvarezii Using Saccharomyces cerevisiae through Deletion of Negative Regulators of GAL Genes

This study was aimed at enhancing galactose consumption from the red seaweed Kappaphycus alvarezii. The optimal pretreatment condition of thermal acid hydrolysis was treated with 350mM HNO3 for 60min at 121°C. The enzymatic saccharification with a 1:1 mixture of Celluclast 1.5L and Viscozyme L showed the maximum yield of glucose; 42-g/L monosaccharide concentration was obtained with the highest yield of pretreatment and enzymatic saccharification (EPS) and the lowest inhibitory compound concentration. The deletion of the GAL80, MIG1, CYC8, or TUP1 gene was performed to improve the galactose consumption rate. The strains with the deletion of the MIG1 gene (mig1Δ) showed higher galactose consumption rate and ethanol yield than other strains. High transcription levels of regulatory genes revealed that the mig1Δ relieved glucose repression. These results show that the mig1Δ enhances galactose consumption rate from K. alvarezii.

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 200mM H2SO4 at 121°C for 60min. Enzymatic saccharification using 16U/mL Viscozyme produced 61.6g/L monosaccharide at 48h. Ethanol productions with ethanol yield coefficients from Azolla weed hydrolysate using Kluyveromyces marxianus, Candida lusitaniae Saccharomyces cerevisiae, and Pichia stipitis were 26.8g/L (YEtOH=0.43), 23.2g/L (YEtOH=0.37), 18.2g/L (YEtOH=0.29), and 13.7g/L (YEtOH=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 60h.

Enhancement of Galactose Uptake from Kappaphycus alvarezii Hydrolysate Using Saccharomyces cerevisiae Through Overexpression of Leloir Pathway Genes.

A total 42.68g/L monosaccharide with 0.10g/L HMF was obtained from 10% (w/v) Kappaphycus alvarezii with thermal acid hydrolysis using 350mM HNO3 at 121°C for 60min and enzymatic saccharification with a 1:1 mixture of Viscozyme L and Celluclast 1.5 L for 72h. To enhance the galactose utilization rate, fermentation was performed with overexpression of GAL1 (galactokinase), GAL7 (galactose-1-phosphate uridyltransferase), GAL10 (UDP-glucose-4-epimerase), and PGM2 (phosphoglucomutase 2) in Saccharomyces cerevisiae CEN.PK2 using CCW12 as a strong promoter. Among the strains, the overexpression of PGM2 showed twofold high galactose utilization rate (URgal) and produced ethanol 1.4-fold more than that of the control. Transcriptional analysis revealed the increase of PGM2 transcription level leading to enhance glucose-6-phosphate and fructose-6-phosphate and plays a key role in ensuring a higher glycolytic flux in the PGM2 strain. This finding shows particular importance in biofuel production from seaweed because galactose is one of the major monosaccharides in seaweeds such as K. alvarezii.

Waste paper valorization for bioethanol production: Pretreatment and acid hydrolysis optimization

ABSTRACT The dramatic fluctuations of oil cost and climate change have together concentrated political and scientific attention on the search of alternative fuels. The aim of this work is to recycle waste paper for producing bioethanol. The production process includes two main stages: the conversion of polysaccharides into simple sugars and the fermentation of these sugars into ethanol. In order to maximize the total sugars content, the parameters of both thermal pretreatment and acid hydrolysis steps are optimized by using the response surface methodology combined with Box–Behnken design. In the thermal pretreatment stage, temperature (100–140°C), residence time (20–60 min), and paper–water ratio (0.5–1.5% w/v) are adjusted. For acid hydrolysis step, temperature (60–100°C), reaction time (20–60 min), and amount of sulfuric acid (1–3% v/v) are the investigated parameters. Total sugars evolution is monitored during fermentation reaction using the yeast Saccharomyces cerevisiae under the optimal parameters of both pretreatment and acid hydrolysis steps. The optimum of thermal pretreatment step was found for the following operation conditions: Temperature = 100.46°C, time = 20.11 min, and paper–water ratio = 1.45% (w/v) with a yield of 48.69% (w/v) of total sugars while the best conditions for the acid hydrolysis step: Temperature = 96.31°C, time = 20.64 min, and amount of sulfuric acid = 1% (v/v), which led to a yield of 79.65% (w/v) of total sugars. Moreover, physicochemical and thermodynamic characteristics of the produced bioethanol (purity degree of 90% v/v) have shown a good agreement with the standards.

Enhanced Bioethanol Fermentation by Sonication Using Three Yeasts Species and Kariba Weed (Salvinia molesta) as Biomass Collected from Lake Victoria, Uganda.

Kariba weed (Salvinia molesta) was used as biomass feedstock for ethanol production by separate hydrolysis and fermentation (SHF). Monosaccharides from Kariba weed hydrolysate were produced using thermal acid hydrolysis, sonication, and enzymatic saccharification. The optimal conditions for thermal acid hydrolysis of 12% (w/v) Kariba weed slurry were evaluated as 200mM HNO3 at 121°C for 60min yielding 10.2g/L monosaccharides. Sonication for 45min before enzymatic saccharification yielded more monosaccharides to 18.7g/L. Enzymatic saccharification with 16U/mL Cellic CTec2 produced 35.4g/L monosaccharides. Fermentation was performed using Saccharomyces cerevisiae, Kluyveromyces marxianus, or Pichia stipitis with sonicated Kariba weed hydrolysate. The control fermentations were carried out using Kariba weed hydrolysate without sonication. The improvement of ethanol production from sonicated Kariba weed hydrolysate using P. stipitis produced 15.9g/L ethanol with ethanol yield coefficient YEtOH = 0.45, K. marxianus produced 14.7g/L ethanol with YEtOH = 0.41. S. cerevisiae produced the lowest yield of 13.2g/L ethanol with YEtOH = 0.37 as it utilized only glucose not xylose. Sonication of Kariba weed was essential in the ethanol production to enhance the productivity of monosaccharides. P. stipitis was determined as the best yeast species using hydrolysates with the mixture of glucose and xylose to produce ethanol.

Comparison study of lignin-kraft extraction process from black liquor using centrifuge and thermal acid hydrolysis methods

Black liquor is a remnant of pulping fluid which generally consists of 14-18 percent solids which is commonly known as weak black liquor (WBL) with a pH of 12 or more. About 65 percent of the solids contained in black liquor are organic compounds derived from wood such as lignin, resins and fatty acids, acids from carbohydrates, and other organic compounds; The remaining 35percent percent is white liquor which is used in the pulping process. Kraft lignin, also called sulfate or alkali lignin, is obtained from black liquor by the extraction method using an acid hydrolysis process, so that pure kraft lignin compounds can be obtained which can be further utilized in various industrial activities. This study is comparing two kraft lignin extraction methods of acid hydrolysis process with thermal assistance (heating temperature) and a gradual centrifuge. The experiment results showed that the levels of lignin contained in black liquor consist of total calories of 391 kcal / Kg which can be processed into energy sources in the recovery boiler unit in further process. The result of kraft lignin extraction process using the acid hydrolysis method with gradual centrifuge stage is better than the thermal acid hydrolysis method. Quantitatively calculated with ASL values difference of around 0.002 mg / g of both the method and the AIR Value using centrifuge give an average yield of 969.815 mg / g, while using thermal assistance gives an average yield of 679.790 mg / g. Qualitatively, the centrifuge method is more optimal compared to the thermal method shown by the results of ICP, FTIR and SEM testing.

R-phycoerythrin, R-phycocyanin and ABE production from Gelidium amansii by Clostridium acetobutylicum

Abstract The red seaweed, Gelidium amansii, contains proteins such as R-phycoerythrin and R-phycocyanin, as well as polysaccharides. Initial protein extraction from G. amansii yielded 53 μg/g R-phycoerythrin and 56 μg/g R-phycocyanin. After protein extraction, monosaccharides were produced using hyper thermal acid hydrolysis and enzymatic saccharification. Acetone–butanol–ethanol (ABE) was produced by Clostridium acetobutylicum KCTC 1790. To overcome the different pH requirements for monosaccharide consumption and solvent production, a two-stage pH control culture strategy was developed. Fermentation at pH 6.0 supported a high cell growth rate and both glucose and galactose were consumed completely. The pH was then shifted from 6.0 to 4.5 to produce ABE after 84 h. The maximum ABE concentration reached 15.5 g/L in comparison to 3.1 g/L under fermentation without pH control. The two-stage pH control strategy is a suitable method for ABE production from G. amansii.

Rapid thermal-acid hydrolysis of spiramycin by silicotungstic acid under microwave irradiation

Spiramycin is a widely used macrolide antibiotic and exists at high concentration in production wastewater. A thermal-acid hydrolytic pretreatment using silicotungstic acid (STA) under microwave (MW) irradiation was suggested to mitigate spiramycin from production wastewater. Positive correlations were observed between STA dosage, MW power, interaction time and the hydrolytic removal efficiencies, and an integrative equation was generalized quantitively. Rapid and complete removal 100 mg/L of spiramycin was achieved after 8 min of reaction with 1.0 g/L of STA under 200 W of MW irradiation, comparing to 30.1% by MW irradiation or 15.9% by STA alone. The synergetic effects of STA and MW irradiation were originated from the dissociated-proton catalysis by STA and the dipolar rotation heating effect of MW. STA performed much better than the mineral acid H2SO4 under MW, due to the much stronger Brönsted acidity and higher Hammett acidity. After 8 min, 98.0% of antibacterial potency was also reduced. The m/z 558.8614 fragment (P1) and m/z 448.1323 fragment (P2) were identified as the primary products, which were formed by breaking glucosidic bonds and losing mycarose and forosamine for P1 and further mycaminose moiety for P2. Finally, production wastewater with 433 mg/L of spiramycin was effectively treated using this thermal-acid hydrolytic method. Spiramycin and its antibacterial potency both dropped to 0 after 6 min. The potency drop was supposed from the losing of mycarose and/or forosamine. To decrease both the concentration of spiramycin and its antibacterial potency, combinedly using STA and MW was suggested in this work to break down the structural bonds of the functional groups rather than to destroy the whole antibiotic molecules. It is promising for pretreating spiramycin-contained production wastewater to mitigate both the antibiotic and its antibacterial potency.