Acid Pretreatment Hydrolysis Research Articles

Study of Avian Colibacillosis and Antimicrobial Resistance in Escherichia coli from Chickens (Gallus domesticus) in Maiduguri, Borno State, Nigeria

Bioethanol is a renewable, colorless, less toxic, and readily biodegradable form of fuel from biological sources; that can be used for heat, electricity, and fuel. In this research study, an alternative feedstock known as microalgae was used. Bioethanol was produced from microalgae using enzymatic hydrolysis. The microalgae was pretreated with acid and alkaline. Hydrolysis was carried out by Aspergillus niger and Saccharomyces cerevisiae was used for fermentation. The concentration of the Bioethanol produced was determined using acid Potassium Dichromate. After hydrolysis, the reducing sugar concentration was determined using Dinitrosalicylic acid (DNS) colorimetric method. Results showed that there was significant difference at p<0.05 in the yields of the reducing sugar produced between acid and alkaline pretreated samples after microbial hydrolysis. Microbial hydrolysis of alkaline pretreated samples was higher in yield. Also, the results showed that the highest bioethanol yield of 0.142ml/l was obtained after alkaline pretreated hydrolysates were fermented with Saccharomyces cerevisiae at 40°C and pH of 6.0. The highest bioethanol yield of 0.116ml/l was obtained from the acid pretreated hydrolysates at 35°C and pH of 5.5. The volatile compounds produced by alkaline pre-treated samples using Gas Chromatography Mass Spectroscopy (GCMS) shows that Ethanol and Di-n-decylsulfone were the highest volatile compounds with peak areas of 30.70% and 41.87% respectively while 2-hydroxy-1-(hydroxymethyl) ethyl ester (linolenic acid) was found to be least volatile compound with peak area of 3.34%.Tthe volatile compounds produced by acid pre-treated samples shows that 2-ethyl-2-methyltridecanol was the highest volatile compound with peak area of 23.00% while Heptacosane was found to be the least volatile compound with peak area of 1.90%. Therefore bioethanol production using alkaline pretreated samples produced a large quantity of bioethanol and may be a preferred method. This study concluded that Microalgae is a suitable substrate for bioethanol production and hydrolyzing with Aspergillus niger and optimization of fermentation conditions at pH 6.0 and 40oC yielded higher bioethanol concentration.

Optimizing cultural conditions and pretreatment for high-value single-cell protein from vegetable waste

The study aimed to produce single-cell protein (SCP) from vegetable waste through solid-state fermentation (SSF) using tomato, capsicum, eggplant, and cucumber waste. Three yeast strains, namely Candida tropicalis, Candida krusei, and Saccharomyces cerevisiae were selected to optimize cultural conditions without pretreatment of the substrate to obtain a higher yield of SCP. The study identified the best-performing yeast strains and optimized the acid and thermal hydrolysis pretreatment of vegetable waste using central composite design by response surface methodology. The substrate was pretreated with varying concentrations of sulfuric acid (2 %, 4 %, and 6 % w/v) at temperatures of 120°C, 140°C, and 160°C. The study demonstrated that SCP production could be enhanced with the acid and thermal hydrolysis of nutrient-supplemented vegetable waste by using optimized cultural conditions. Without pretreatment of vegetable waste, the yeast combination of Saccharomyces cerevisiae and Candida tropicalis achieved a maximum protein content of 10.8 mg/g of dry biomass (an increment of 63.6 % compared to control). With the same yeast strains, pretreatment of vegetable waste (with 4 % sulfuric acid at 140°C) and supplemented with a nutrient source increased SCP production to 21.9 and 31.7 mg/g (an increment of 231.8 % and 375.8 % compared to control), respectively. The study's findings suggest that SCP production from vegetable waste can be optimized through SSF and acid-thermal hydrolysis pretreatment, which could be a promising approach for efficient waste management.

Application of Microwave Energy to Biomass: A Comprehensive Review of Microwave-Assisted Technologies, Optimization Parameters, and the Strengths and Weaknesses

This review article focuses on the application of microwave-assisted techniques in various processes, including microwave-assisted extraction, microwave-assisted pyrolysis, microwave-assisted acid hydrolysis, microwave-assisted organosolv, and microwave-assisted hydrothermal pretreatment. This article discusses the mechanisms behind these techniques and their potential for increasing yield, producing more selectivity, and lowering reaction times while reducing energy usage. It also highlights the advantages and disadvantages of each process and emphasizes the need for further research to scale the processes and optimize conditions for industrial applications. A specific case study is presented on the pretreatment of coffee waste, demonstrating how the choice of microwave-assisted processes can lead to different by-products depending on the initial composition of the biomass.

Novel approach for corn straw biorefineries: Production of xylooligosaccharides, lignin and ethanol by nicotinic acid hydrolysis and pentanol pretreatment

The productive separation and conversion of corn straw offers significant prospects for the economic viability of biorefineries centered on straw resources. In this work, a graded utilization method was proposed to produce xylo-oligosaccharides (XOS), ethanol and lignin from corn straw by nicotinic acid (NA) hydrolysis and water/pentanol pretreatment. A XOS yield of 52.6 % was achieved under optimized conditions of 100 mM NA, 170 °C and 30 min. The solid residue was directly treated with water/pentanol, achieving a lignin removal rate of 79.7 %, and the total XOS yield was improved to 62.6 %. The lignin recovered from pentanol had a high purity of 97.6 %, with high phenolic OH content. Simultaneous saccharification and fermentation of final residue resulted in an ethanol yield of 92.0 %, which yielded 55.3 g/L ethanol. Thus, NA hydrolysis and water/pentanol pretreatment provided an efficient, environmentally friendly approach to fractionate corn straw for the co-production of XOS, ethanol, and lignin.

Cellulose Nanocrystal Preparation via Rapid Hydrolysis of Wood Cellulose Fibers Using Recyclable Molten Ferric Chloride Hexahydrate

Cellulose nanocrystals (CNCs) are clean and sustainable materials that have drawn significant attention in academia and industry because of their unique physicochemical properties. However, realizing economical and environmentally friendly production of CNCs remains a challenge. In this study, we proposed an innovative strategy to fabricate CNCs, which involves the acid hydrolysis pretreatment of wood cellulose fibers using innocuous and recyclable ferric chloride hexahydrate (FeCl3·6H2O). During the molten FeCl3·6H2O treatment, the degree of polymerization (DP) of the cellulose fibers sharply decreased, along with the transformation of cellulose I to cellulose II crystallites. Molten FeCl3·6H2O quickly hydrolyzed cellulose fibers within 5 min at 80 °C, inducing a rapid decrease in the DP from 922 to 196, and the water-insoluble solid (WIS) retention reached 80.1%. CNCs were successfully produced from the mechanical disintegration of the WIS with a low energy input. Hence, the yield of CNCs is consistent with that of the WIS. Interestingly, the CNCs exhibited typical cellulose II crystallites, which were significantly different from those of the cellulose feedstock (cellulose I). Detailed characterization revealed that the CNCs had tunable number-averaged heights of 10.4–26.9 nm and high thermal stability (a maximal weight loss temperature of 327 °C). Most notably, FeCl3·6H2O was easily recycled from the hydrolysate after hydrolysis, with a high recovery of 94.0–94.5 wt %, using simple concentration and crystallization technologies. Thus, this study proposes a novel production technology for CNCs that is both economical and eco-friendly, providing new ideas for clean and large-scale production of CNCs.

Integration of extraction and acid hydrolysis processes as a strategy for better use and obtaining products from coffee residues

The present study used a mixture of coffee processing residues to develop integrated processing for extracting high-value compounds with solvents and acid hydrolysis. The waste mixture comprised 55% bagasse, 40% husk, and 5% parchment. The physicochemical characterization showed 9.39 ± 0.37% of soluble fraction, and 90.61 ± 0.37% of the insoluble fraction, of which 60.41 ± 0.67% was cellulose, 6.44 ± 1.32% was hemicellulose and 23.21 ± 0.29% was lignin. In the first stage, the treatments of Organosolv and Organosolv assisted with ultrasonic (OAU) were applied at three particle sizes. The maximum yields of polyphenols were obtained with the smallest particle size and were 11.32 ± 0.63 mg GAE (gallic acid equivalents)/g DW (dry weight) for Organosolv and 10.12 ± 0.55 mg GAE/g DW for OAU. The best results for carbohydrate release were obtained with acid hydrolysis (0.5 % H2SO4) and OAU pretreatment. Principal component analysis indicated that the OAU treatment with hydrolysis at 15 psi was the best to obtain polyphenols, arabinose, and xylose.

Optimisation of Bioethanol Production in a Potato Processing Industry

Nowadays, there is a requirement for industries to eliminate carbon from their energy mix and substitute it with greener options. This calls for investment in efforts to facilitate the scaling up of technical advancements. Because of the huge amount of waste, a life cycle strategy has been used by industries, especially the food industry, to lessen the environmental impact of their products. One of the sectors that burdens the environment with a significant amount of waste is the potato processing industrial sector. The current study focuses on the valorisation of all the potato processing waste streams (potato peels, potato tubers and slices, starch and low-quality chips) towards bioethanol production at a pilot level. After their physico-chemical characterisations, several experimental trials were performed in order to determine the optimum pretreatment and hydrolysis conditions for each waste stream. Acid hydrolysis, alkaline hydrolysis and hydrothermal pretreatment were examined when no pretreatment resulted in low ethanol yields (below 60%). The optimum results that were obtained were applied in a pilot plant of 200L to examine the upscaling factor. It was verified that upscaling by 1000 times generates comparable and, in some cases, greater results. From the integration of the results and the mass balances of a typical potato processing company, a full-scale implementation plan was also set up, where it was calculated that around 2 m3 bioethanol per week could be produced.

High Cellulose Purity by Acid Hydrolysis Pretreatment on Kenaf Outer Bast

Acid hydrolysis treatment of kenaf outer bast fiber can produce pure cellulose content and hydrolyzed hemicellulose to monosaccharides. The effects of various reaction temperatures (110–130 °C), acid concentrations of sulfuric acid (0.25–1.00 N), and reaction times (60–120 min) were investigated as the optimum condition to gain pure cellulose content. A 1H NMR spectroscopy was used to analyze the carbohydrate content in the reaction of acid hydrolysis treatment. The results showed that optimum conditions for acid hydrolysis refer to two treatment prospects. First, a higher reaction temperature of 130 °C was necessary to increase the reaction for the hydrolyzes of hemicellulose—the high yield content produced by 0.25 N sulfuric acid with a short reaction time of 60 min. to improve the purity of cellulose, provided by the high sulfuric acid solution of 1.00 N for 120 min. Hemicellulose was hydrolyzed at almost 100% based on the two optimal conditions. The analysis revealed that a high temperature of acid hydrolysis was the primary treatment to hydrolyze hemicellulose to increase high pure cellulose from the kenaf outer bast fiber.

Effective fractionation of microalgae biomass as an initial step for its utilization as a bioenergy feedstock

• S. obliquus was effectively fractionated by mild (un)catalyzed hydrothermal processes. • Soluble sugars were mainly present as soluble oligosaccharides. • Protein was mainly retained in the solid fraction. • Dilute acid hydrolysis allowed higher oligosaccharides yield at mild conditions. • Co-production of added-value oligosaccharides in marine biorefineries. Scenedesmus obliquus , a biotechnologically recognized microalga, was grown in 70 L vertical photobioreactors using non-supplemented secondary brewery wastewater as a culture medium. Upon collection, by mechanical means, the cells were subjected to hydrothermal (autohydrolysis) and dilute acid hydrolysis (0.5% sulfuric acid) pre-treatments were carried out using pressure micro-reactors under isothermal conditions up to 300 min. Both processes enabled a high recovery of soluble sugars (∼50%) that were, in a great majority, present in the added-value oligomeric form (92% and 90.5% for autohydrolysis and dilute acid hydrolysis, respectively). Protein solubilization also presented relevant yields (35% removal), with dilute acid hydrolysis allowing both higher oligosaccharides and protein productivities at a milder temperature. As compared to the current whole microalgae biomass-based upgrade strategies, the use of these mild processes is extremely promising, as they will enable the future co-production of added-value oligosaccharides, and protein, which can be relevant co-products of a biofuels-based biorefinery.

Different Preparation Method of Nanocellulose from Macaranga gigantea and Its Preliminary Study on Packaging Film Potential

Nanocellulose is a versatile cellulosic nanomaterial that can be used in many application areas. Applying different preparation strategies leads to different types of nanocellulose. In this study, nanocrystalline cellulose (NCC) and nanofibrillated cellulose (NFC) were prepared from lesser known wood species, viz., Macaranga gigantea, using sulfuric acid hydrolysis and enzymatic pretreatment with ultrafine grinding approaches, respectively. The respective nanocellulose was characterized by means of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), atomic force microscopy (AFM). It was then converted into a thin film to assess its performance which includes tensile test, transparency, air permeance, water vapor transmission rate (WVTR), and water vapor permeability (WVP) properties. NCC and NFC produced from the raw material of Macaranga had average widths of 6.38 ± 3.92 nm and 13.17 ± 12.71 nm, respectively. Peaks in FTIR spectra showed the conversion of Macaranga wood to nanocellulose by the presence of cellulose fingerprint as well as absence of lignin and hemicellulose after alkaline treatment. The successful conversion was also supported by XRD analysis which displayed the increased crystallinity value from 54% to 70%. TGA decomposition pattern at 200-490 °C revealed the thermal stability of the samples. The thin film produced from nanocelluloses had WVTR values of 4.58 and 12.14 g/(day·m2) for NFC and NCC, respectively, comparable to those of films from polyester and oriented polypropylene. Nanocellulose-based thin film has the potential to be used as sustainable and biodegradable packaging.

An integrated process using acetic acid hydrolysis and deep eutectic solvent pretreatment for xylooligosaccharides and monosaccharides production from wheat bran

Organic acid hydrolysis for xylooligosaccharides (XOS) production from lignocelluloses provides the benefits of simple operation, rapid reaction and high XOS yield. However, no literature reported the XOS production from wheat bran (WB) by organic acid hydrolysis. In this paper, acetic acid (AA) hydrolysis was employed to produce XOS from WB. After AA hydrolysis (5 %, v/v, 170 °C, 20 min) of 100 g/L WB, the concentrations of X2, X3, X4, X5 and X6 were 2.4, 5.0, 1.9, 1.9 and 1.4 g/L respectively and the total XOS yield was 62.9 %, which was the highest among the previous researches. The arabinose yield reached 76.1 %. Then, AA-hydrolyzed WB was delignified by deep eutectic solvent (DES) pretreatment and the resulting residue had the glucose and xylose yields of 83.8 % and 54.8 %, respectively. This work offers a productive method for the conversion of WB into XOS, arabinose and glucose by AA hydrolysis and DES pretreatment.

Hidrólisis ácida de hemicelulosa de Ipomoea arborecens: Cinética de producción de xilosa

In this paper the composition change of Ipomoea arborescens was evaluated under acid hydrolysis pretreatment, and the kinetic parameters of this reaction were determined. The goal was to evaluate the effects of particle size in the reaction rate of hemicellulose hydrolysis, and to find the concentration of sulfuric acid in which the reaction mechanism favors hemicellulose hydrolysis of Ipomoea arborescens particles. Once the best conditions were found, Ipomoea arborescens particles were hydrolyzed at different temperatures. A pseudo-homogenous model was adopted to describe hemicellulose hydrolysis. The empirical formula of hemicellulose was determined experimentally to have 21 molecules of xylose, 5 molecules of glucose and 1 molecule of galactose. The mathematical model of hemicellulose hydrolysis is successful to describe the experimental results when the temperature is between 120 and 160°C.

Cardoon Hydrolysate Detoxification by Activated Carbon or Membranes System for Bioethanol Production

Advanced biofuels incorporation into the transportation sector, particularly cellulosic bioethanol, is crucial for attaining carbon neutrality by 2050, contributing to climate changes mitigation and wastes minimization. The world needs biofuel to be commercially available to tackle the socioeconomic challenges coming from the continued use of fossil fuels. Cynara cardunculus (cardoon) is a cheap lignocellulosic raw biomass that easily grows in Mediterraneous soils and is a potential renewable resource for a biorefinery. This work aimed to study the bioethanol production from cardoon hemicellulosic hydrolysates, which originated from dilute sulfuric acid hydrolysis pretreatment. A detoxification step to remove released microbial fermentative inhibitors was evaluated by using both activated carbon adsorption and a nanofiltration membrane system. The Scheffersomyces stipitis CBS5773 yeast and the modified Escherichia coli MS04 fermentation performances at different experimental conditions were compared. The promising results with E. coli, using detoxified cardoon by membrane nanofiltration, led to a bioethanol volumetric productivity of 0.30 g·L−1·h−1, with a conversion efficiency of 94.5%. Regarding the S. stipitis, in similar fermentation conditions, volumetric productivity of 0.091 g·L−1·h−1 with a conversion efficiency of 64.9% was obtained. Concluding, the production of bioethanol through detoxification of hemicellulosic cardoon hydrolysate presents a suitable alternative for the production of second-generation bioethanol, especially using the modified E. coli.

Sequential detoxification of oil palm fronds hydrolysate with coconut shell activated charcoal and pH controlled in bioreactor for xylitol production

Acid hydrolysis pre-treatment on biomass produces furan derivatives, phenolics, and organic acids, which are harmful to the fermenting microorganisms. Removal of inhibitor compounds from the hydrolysate using coconut shell activated charcoal (CSAC) adsorption is essential to improve the quality of detoxified hydrolysate as a feedstock for xylitol production. This study investigated adsorption parameters of different pH (pH 1–7), temperature (17.5–92.5 °C), CSAC-to-hydrolysate loading (0.5–9.5% (w/v)) and contact time (30–142.5 min) using a central composite design (CCD) to evaluate the interactive effect of the adsorption process parameters on response variables. Under optimal adsorption process (pH 2.5, 55.6 °C, 5.3% (w/v) and 74 min), the results demonstrated loss of 10.4% sugar and 12.8 % of detoxified hydrolysate volume with 79.9% of furfural removal. Inhibition by acetic acid could be alleviated by pH control in bioreactor since the concentration of acetic acid was decreased by up to 73.7% at the end of OPF hydrolysate fermentation. The fermentability test using detoxified OPF hydrolysate by Kluyveromyces marxianus ATCC 36907 demonstrated 78% higher xylitol production compared to non-detoxified OPF hydrolysate. This finding corroborates that this sequential detoxification is a promising method to enhance the xylitol production using OPF hydrolysate.

Dilute Acid Hydrolysis of Jute Bast Fiber for Selected Xylan Removal

Jute fiber was proposed as an alternative raw material for dissolving pulp production. Jute fiber had cellulose (71.8%±0.1%), xylan (10.8%±0.1%), lignin (13.7%±0.2%), and extractives (3.8%±0.0%). In this study, jute fiber was hydrolyzed with H₂SO₄ to remove xylan. To achieve the best conditions for removing hemicellulose and obtaining a high cellulose content, acid hydrolysis pretreatment was performed at various acid concentrations (0.25-1 N), reaction times (60-120 min), and temperatures (100°C-120°C). The results showed that the optimum condition of acid hydrolysis for higher dissolving pulp raw material yield within less than 5.0% xylan was cellulose (60.5±0.2) and xylan (2.9±0.2) at 1 N H₂SO₄, 100°C for 90 min. However, by increasing the reaction temperature to 120°C for 120 min, the chemical used was reduced to 0.25 N H₂SO₄ and the highest purity of cellulose was produced, with cellulose and xylan content of 56.1%±0.1% and 1.3%±0.1%, respectively.

Process Development for the Detoxification of Fermentation Inhibitors from Acid Pretreated Microalgae Hydrolysate.

The aim of this study was to remove 5-hydroxymethyl furfural (5-HMF) and furfural, known as fermentation inhibitors, in acid pretreated hydrolysates (APH) obtained from Scenedesmus obliquus using activated carbon. Microwave-assisted pretreatment was used to produce APH containing glucose, xylose, and fermentation inhibitors (5-HMF, furfural). The response surface methodology was applied to optimize key detoxification variables such as temperature (16.5–58.5 °C), time (0.5–5.5 h), and solid–liquid (S-L) ratio of activated carbon (0.6–7.4 w/v%). Three variables showed significant effects on the removal of fermentation inhibitors. The optimum detoxification conditions with the maximum removal of fermentation inhibitors and the minimum loss of sugars (glucose and xylose) were as follows: temperature of 36.6 °C, extraction time of 3.86 h, and S-L ratio of 3.3 w/v%. Under these conditions, removal of 5-HMF, furfural, and sugars were 71.6, 83.1, and 2.44%, respectively, which agreed closely with the predicted values. When the APH and detoxified APH were used for ethanol fermentation by S. cerevisiae, the ethanol produced was 38.5% and 84.5% of the theoretical yields, respectively, which confirmed that detoxification using activated carbon was effective in removing fermentation inhibitors and increasing fermentation yield without significant removal of fermentable sugars.

Dilute acid hydrolysis pretreatment for sugar and organic acid production from pineapple residues

Pineapple residue which is pineapple leaves composed of about 80% of carbohydrate containing lignin, cellulose and hemicellulose was utilised for the production of fermentable sugars. However, pretreatment of lignocellulosic material is required to remove hemicellulose and lignin and reducing crystallinity of cellulose to enhance hydrolysis. This paper presents an experimental study of acid hydrolysis pretreatment in pineapple residue to produce sugar and organic acid using sulphuric acid. The effect of different acid concentration (4%, 8% and 12% v/v), solid-to-liquid ratio (10%, 15% and 20% w/v) and reaction time (40, 80, and 120 minutes) of acid hydrolysis pretreatment on pineapple residue at temperature of 100°C were studied to produce high yield of sugar and low organic acid production. As a result, the highest of sugar concentration simultaneously with the lowest of organic acids concentration from pineapple residue were 2.68 ± 0.12 g/L (xylose), 8.84 ± 0.11 g/L (glucose), 1.62 ± 0.20 g/L (formic acid) and 3.28 ± 0.26 g/L (acetic acid); recorded at conditions of 12% acid concentration (v/v), 20% solid-to-liquid ratio and 80 minutes of reaction time. In conclusion, dilute acid hydrolysis pretreatment was a great approach in order to produce high sugar at the same time with low organic acids yield from pineapple residue at mild conditions.

Optimization on fermentation of seaweed (Gracilaria sp.) as feedstock for bioethanol production by Saccharomyces cerevisiae

In this study, dried seaweed (Gracilaria sp.), a red algae was used as feedstock for the production of bioethanol due to its high carbohydrate content (76.67 %). Dried seaweed is hydrolysed into reducing sugar by using dilute acid hydrolysis pre-treatment at optimized conditions (0.1 M sulphuric acid (H2SO4), 121 °C, 30 minutes) and able to obtain 18.438 g/L of reducing sugar. This hydrolysate is converted into bioethanol by Saccharomyces cerevisiae via fermentation. Two significant factors, namely, fermentation temperature and medium pH were screened by performing One-Factor-At-A-Time (OFAT) analysis. The first factor manipulated was the fermentation temperature (40-50 °C at pH 4.5), followed by medium pH (pH 4.0-5.0 at 45 °C). Ethanol with concentration of 3.4202 g/L was successfully obtained from OFAT analysis under condition of 45 °C and pH 4.5. The significant factors were then statistically optimized using Central Composite Design (CCD) in Response Surface Methodology (RSM). From the data analyzed from Design of Experiment (DoE), at its optimum fermentation conditions (44.83 °C and pH 4.48), the maximal ethanol production obtained is 3.8395 g/L. A validation test with triplicate was performed to validate the actual with predicted value and result in ±1.49% deviation is accepted.

Efficient biobutanol production from potato peel wastes by separate and simultaneous inhibitors removal and pretreatment

Abstract Potato peel waste (PPW) is a carbohydrate-rich waste from potato industries, which is an environmental threat worldwide. In this study, it was evaluated for biobutanol production via acetone-butanol-ethanol fermentation by Clostridium acetobutylicum. The results showed that PPW contained a considerable amount of glycoalkaloids, severe inhibitors for the bacterium. Thus, three processes, i.e., dilute acid pretreatment (Process I), the inhibitors extraction followed by dilute acid hydrolysis (Process II) and ethanol organosolv pretreatment (Process III), were employed before hydrolysis and fermentation to produce ABE. The extraction of glycoalkaloids with ethanol, dilute acid hydrolysis at 180 °C for 60 min, and enzymatic hydrolysis led to a hydrolysate with 36 g/L glucose, which was successfully fermented to 11.6 g/L ABE. In process II, the organosolv pretreatment led to the removal of the major fraction of inhibitors, in the range of 77–88% of glycoalkaloids. The enzymatic hydrolysis of PPW pretreated with 75% ethanol at 180 °C for 60 min resulted in a fermentable hydrolysate with 38 g/L glucose. The fermentation of overall hydrolysate resulted in a high ABE concentration of 24.8 g/L, indicating that PPW is an appropriate substrate for butanol production after the removal of its bacterial inhibitors.

Sustainable valorization of paper mill sludge into cellulose nanofibrils and cellulose nanopaper

As a kind of agro-industrial wastes, paper mill sludge (PMS) has posed serious environmental and economic challenges for disposal due to the more stringent regulations and diminishing land availability in recent years. The present study is aimed at providing a sustainable approach to efficiently convert PMS to cellulose nanofibrils (CNFs) and cellulose nanopaper (CNP) by formic acid (FA) hydrolysis pretreatment and the followed microfluidization. It is found that FA hydrolysis (4–6 h) could swell and shorten PMS fibers, and only two-pass microfluidization is sufficient to get uniform CNFs from the collected cellulose residual. Results indicate that the obtained CNFs show high thermal stability and crystallinity index, surface functionality (ester groups), as well as a high yield of over 75 wt.%. Notably, more than 90 % FA can be recovered and the hydrolyzed sugars could be potentially used to produce platform chemicals (e.g. lactic acid, furfural). Finally, transparent CNP is prepared from the CNFs suspension via a simple vacuum filtration technique. The resultant CNP shows good mechanical properties with the maximum tensile strength and toughness of 106.4 MPa and 6.62 MJ/m3, respectively. Therefore, the current work provides a green and sustainable method to valorize PMS for the production of valuable CNFs and CNP.