Acid Hydrolysis Research Articles

Bioaccessibility of bioactive compounds present in Persea americana Mill. seed ingredient during oral-gastric digestion with antibacterial capacity against Helicobacter pylori

Ethnopharmacological relevanceIn ancient Mexican cultures, the Persea americana Mill seed has been used against gastrointestinal diseases, due to high concentrations of bioactive compounds. According to Traditional Mexican Medicine, P. americana seed aqueous infusion is used against roundworms, intestinal worms, parasites, and gastrointestinal problems, in a dose taken over three or four days. In addition, Mexican Society of Natural History indicates the traditional use of P. americana seed powder as an antiparasitic, and antibacterial. On the other hand, Helicobacter pylori infection is a factor associated with the development of gastric disease, peptic ulcers as well as some types of gastric lymphomas and gastric cancer in humans; in this way is necessary scientific evidence about P. americana seed effect in gastrointestinal disease. Aim of the studyThe work aimed to evaluate bioactive compounds bioaccessibility and antimicrobial potential against Helicobacter pylori during oral-gastric digestion in vitro of food ingredient from Persea americana Mill. seed and elucidate the possible action mechanism using in silico tools. Materials and methodsInitially, P. americana seed oil and aqueous extract of P. americana seed were obtained using ultrasound and maceration respectively, and the food ingredient from P. americana seed was obtained. The samples underwent oral-gastric digestions by the INFOGEST method, to continue identifying and quantifying the bioactive compounds by HPLC-DAD and GC-MS. The anti-Helicobacter pylori activity determination were used fourteen Helicobacter pylori clinical strains and reference strains by Susceptibility testing by Minimal Inhibition Concentration, Kinetics of Growth Inhibition of H. pylori, Urease Inhibitory Kinetic. Finally, to elucidate a possible action mechanism used in silico tools (Software AutoDock 4.2.6 and BioVia Discovery v.19.1.0.1.18287). ResultsThe lipophilic fraction of P. americana seed detected oleic acid, linoleic acid, and avocadenofuran compounds, and the phenolic fraction showed the presence of catechin, rutin, ellagic, and chlorogenic acid, among others. Phenolic compounds conformational changes during oral-gastric digestion due to mechanical and acid hydrolysis, while lipophilic compounds showed a 20% increase in the gastric phase. Persea americana Mill. seed ingredient (3.08 μg/mL) showed total in vitro inhibition of clinical and reference strains of H. pylori, likewise, the lipophilic fraction had a lower inhibition concentration (2.59 μg/mL) regardless of the strains. Among the mechanisms found in silico, inhibition of target proteins such as CagA, BabA, and MUC5 were observed, as virulence factors involving adherence and bacterial pathogenicity. ConclusionsThis research provides evidence that food ingredient from P. americana seed has antimicrobial in vitro potential against H. pylori clinical strains, through phenolic and mainly lipophilic compounds, opening new scientific evidence that supports the P. americana seed's traditional use.

Continuous co-digestion of sewage sludge and highly concentrated waste bioplastic hydrolyzate without shortening hydraulic retention time

Bioplastics have garnered substantial interest as alternatives to conventional petroleum-based plastics. However, their management and conversion to biogas continues to be significantly challenging. In this study, we evaluated the suitability of various plastics for hydrolysis at 160 °C for 12 h using different solvents. The biogas yield (BGY) of the monomers constituting these plastics and the obtained plastic hydrolyzates was comprehensively evaluated. When water was used as a solvent, 100 % hydrolysis of polylactic acid (PLA) and polybutylene succinate (PBS) was observed. When polybutylene adipate co-terephthalate (PBAT) and polyhydroxybutyrate (PHB) were hydrolyzed with water, the degradation ratio was approximately 30 %; however, using an aqueous lactic acid solution as a solvent improved the degradation ratio to 78 % and 100 %, respectively. In the BGY test of the plastic hydrolyzates, the biogas volumes derived from the hydrolyzates were 563, 461, 337, and 573 mL/g COD-added for PLA, PBS, PBAT, and PHB, respectively. With 1,160 gCOD/L waste PLA hydrolyzate, continuous co-digestion of sewage sludge and the hydrolyzate was conducted. Organic loading rates of sewage sludge and the hydrolyzate were 2.3 and 2.4 gCOD/L/d, respectively. The operation was stable and the methane production volume from the PLA hydrolyzate was 414 L/kgCOD-added. Using highly concentrated PLA hydrolyzate, the hydraulic retention time was 19.3 days, which was only 0.7 days shorter than that of anaerobic digestion of sewage sludge only (20 days). Therefore, highly concentrated PLA hydrolyzate maintains the retention time of normal sewage sludge digestion. Conclusively, the present study has crucial practical implications for plastic waste management.

Influence of Infrared Dry Heat Treatment on the Structure and Properties of Potato Starch

AbstractThe current study presents a novel approach to starch modification using infrared dry heat treatment (IR‐DHT). IR‐heating at 200 °C allows one to reduce the processing time to 15 min and does not lead to irreversible amorphization of starch structure. Upon IR‐DHT, an increase in density of starch granules from 1.4888 ± 0.0005 to 1.5038 ± 0.0005 g cm−3 is observed. The crystallinity degree of the starch exposed in water at 20 °C after IR‐DHT does not change compared to the crystallinity of native starch hydrated at the same temperature. However, the exposure in excess of water of native potato starch at 45 °C induces an increase of crystallinity up to 81% (along with a significant increase in the intensity of the d100 reflection), while heat‐treated starch exposed in water at the same temperature has reduced crystallinity (RC = 39%). In addition, the concentration of soluble carbohydrates released during the exposure process (45 °C, excess of water) increases by an order of magnitude for heat‐treated starch compared to the native sample. Hence, IR‐DHT may become a promising way to influence the processes of acid and enzymatic hydrolysis and control starch properties, such as pasting, solubility, and digestibility.

Fed-batch fermentation of sugarcane biomass applied for biomolecules production in fluidized bed reactor

A production of xylitol and ethanol from a mixture of sugarcane straw and bagasse (biomass composed of 50 % m/m of both) hydrolysates was evaluated in a batch-fed column reactor. The biomass underwent acid hydrolysis, and the xylitol production process from hemicellulosic hydrolysate was assessed to determine the feasibility of operating four batches, showing conversions (YP/S of 0.28, 0.46, 0.57 and 0.47 g/g). Afterwards, alkaline pretreatment was performed, followed by enzymatic saccharification of the remaining biomass to obtain fermentable sugars for ethanol production. This involved operating five cycles, showing YP/S values of 0.14, 0.18, 0.24, 0.38 and 0.37 g/g, respectively. Additionally, the utilization of the black liquor generated from alkaline pretreatment was studied for reuse in subsequent pretreatments, demonstrating the feasibility of 4 cycles and thus, reducing the need for chemical preparation. The potential for maximizing the use of the main fractions of sugarcane biomass was confirmed.

Fumaric acid production by Rhizopus species from acid hydrolysate of oil palm empty fruit bunches.

The hemicellulosic fraction of lignocellulosic biomass is a very important material, due to the significant concentration of pentoses present in its composition and that can be used sustainably in biotechnological processes such as the production of fumaric acid. Research efforts are currently being promoted for the proper disposal and valorization of empty fruit bunches (EFB) from oil palm. In this work, seventeen Rhizopus species were evaluated in a fermentation medium with EFB hydrolyzate, without detoxification, as a carbon source for fumaric acid production. Rhizopus circicans 1475 and Rhizopus 3271 achieved productions of 5.65g.L-1 and 5.25g.L-1 of fumaric acid at 30°C, 120rpm for 96h, respectively. The percentage of consumed sugars, mainly pentoses, was 24.88% and 34.02% for R. circicans 1475 and R 3271, respectively. Soy peptone and ammonium sulfate were evaluated as nitrogen sources, where soy peptone stimulated the formation of biomass pellets while ammonium sulfate produced mycelia and clamps.

Particle Size Modification of Breadfruit Starch (Artocarpus altilis) into Nanoparticle Size Through Top Down Technique using Acid Hydrolysis

<br /><span style="font-size: 9.0pt; line-height: 150%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: AR-SA; mso-bidi-language: AR-SA; mso-bidi-font-style: italic;" lang="EN-US">Breadfruit (<em>Artocarpus altilis</em>) is a significant starch source, comprising up to 70.25% of its composition, and holds extensive industrial applications. However, the physicochemical properties of natural starch pose several challenges to its direct use as an industrial raw material. These challenges include high viscosity, substantial swelling power, low solubility, significant retrogradation, limited digestibility, and poor thermal stability. To address these issues, modification of the starch particle size to the nanometer scale is proposed, which is anticipated to enhance both functional and physicochemical properties. This study employs a top-down approach through 2.2 N HCl acid hydrolysis at 38°C for 24 hours. This method offers simplicity, efficiency for scale-up in industrial applications, and relatively higher stability than alternative approaches. Particle size analysis using Particle Size Analysis (PSA) revealed an average particle size of 215 nm. Fourier Transform Infrared (FT-IR) spectroscopy showed characteristic bands similar to natural starch, with slight variations in peak intensity, indicating successful acid hydrolysis and structural disruption of the molecular order. Morphological analysis revealed minimal changes in the granules' surface structure, with clumping observed due to acid hydrolysis. The resultant starch nanoparticles exhibited decreased viscosity and swelling while solubility was enhanced. Therefore, nanoparticle starch holds promising applications in food and non-food industries</span><span style="font-size: 9.0pt; line-height: 150%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-ID; mso-fareast-language: AR-SA; mso-bidi-language: AR-SA; mso-bidi-font-style: italic;">.</span>

Chemical Hydrolysis-Gamma Irradiation Processes for Cellulose Nanofibers Isolation from Rice Straw

Utilization of agriculture biomass waste into high value product is still potential to develop. In this study, cellulose nanofibers (CNF) as valuable materials were isolated from rice straw. Sodium hydroxide pulping and hydrogen peroxide bleaching were conducted as cellulose pretreatment. The CNF was prepared using 1 M hydrochloric acid hydrolysis followed gamma irradiation with various radiation doses, i.e. 40, 60, 80, 100 and 120 kGy. Compositions of α–cellulose and water retention of each stage processes increased inversely with hemicellulose, lignin and degrees of polymerization which had been strengthened by Fourier transform infrared spectroscopy (FTIR) spectra. X-ray Diffraction (XRD) analysis revealed that crystallinity index was more intense than rice straw, i.e. 80.85 %. Particle Size Analyzer (PSA) studies described the isolation process of CNF succeed with the smallest size 77.8 nm. The CNF functional groups of hydrophilic both hydroxyl and carboxylate slightly diminished with increasing of radiation doses followed water retention reducing, however the crystallinity had not changed significantly. Increasing radiation doses also could improve the thermal stability with the highest Tg 153.1 0C therefore the obtained CNF could be used as suitable nanocomposite.

Effect of amylose partial extraction on citrate esterification of potato starch and its role in structure and physicochemical modification

This study examines the impact and influence of amylose on the starch esterification reaction through partial extraction of amylose. Citric acid was added for the esterification reaction, and then the esterified starches' multiscale structure, physicochemical, and functional properties were evaluated. As the extraction time of amylose increased, the amylose content in the starch decreased. Higher concentrations of citric acid will lead to samples with a higher degree of substitution, with DS rising from 0.203 % (0 h) to 0.231 % (3.5 h) at CA3 treatment. While removing amylose had minimal effects on the crystal structure of starch granules, it did decrease the ratio of A and B1 chains and the molecular weight of amylose. Acid hydrolysis exacerbated these changes upon the addition of citric acid. Furthermore, removing amylose followed by citrate esterification resulted in lower pasting viscosity, enthalpy of gelatinization (from 13.37 J to 2.83 J), and degree of short-range ordering. Also, digestion shows a decrease caused by the increasing content of slow-digesting starch. The presence of amylose in starch granules does affect the formation of starch esters, and removing it before esterification modification may improve production efficiency and reduce costs to some extent.

A simple method for the quantification of amidic bioavailable dissolved organic nitrogen in seawater

AbstractA targeted method for the quantification of bioavailable amide N found in marine DON (bDON) is presented. The method utilizes mild acid hydrolysis to convert amide N found in proteins and N‐acetyl amino polysaccharides to primary amine containing products that are measured using a highly sensitive (nanomolar range and precision) fluorometric technique with addition of O‐phthaldialdehyde. We find amidic bDON concentrations ranging from 0.08 to 1.82 μM N within waters from the upper 300 m in the southern California Current, Southern California Bight, and subtropical North Pacific representing 15–33% of bulk DON concentrations. Bioassay experiments from the North Pacific revealed consumption of ~20% of the in situ bDON within 5 days. The method represents a simple and rapid tool for the quantification of bioavailable DON concentrations in seawater with improved analytical precision over traditional estimates of bulk DON concentrations.

Sensitive, precise fingerprint profiling for monosaccharide analysis of Bacillus Calmette-Guérin polysaccharide and nucleic acid isolates

A sensitive and precise HPLC-DAD method with pre-column PMP derivatization was established and validated, for analyzing the polysaccharides in Bacillus Calmette-Guérin polysaccharide and nucleic acid (BCG-PSN) isolates, after acid hydrolysis. And the HPLC fingerprint profiling was used to analyze its monosaccharide composition. The monosaccharide concentration-peak area calibration curve was of good linearity (R2 > 0.99), over the range of 0.016–0.08 mg/mL for mannose or 0.24–1.20 mg/mL for glucose, with high recovery of 93–105 % for quality control samples. The intra-day RSD values of mannose and glucose concentration were less than 2.5 % and 2.1 %, respectively, and their inter-day RSD values were less than 4.3 % and 2.2 %, respectively, and remained stable for up to 14 days. This method also remained durable against changes in chromatographic parameters, but it's susceptible to the flow rate of mobile phase. Additionally, the method was applied to analyze the content of mannose and glucose in 22 batches BCG-PSN powder and 17 batches BCG-PSN injection. The results showed that the HPLC-DAD fingerprint spectra of all the BCG-PSN powder and BCG-PSN injection samples had a high degree of similarity, with the similar indexes up to 0.999 and 0.998, respectively. The HPLC-DAD method with pre-column PMP derivatization is highly rapid, effective, visual, and accurate for determination of monosaccharide contents. The validated method was successfully applied to the analysis of polysaccharide in both BCG-PSN powder and injection.

Life cycle assessment of cellulose nanocrystals prepared from crop straw by sequential periodate-chlorite oxidation

Life cycle assessment (LCA) of cellulose nanocrystals (CNC) prepared by sequential periodate-chlorite oxidation (SPCO) remains limited. In this study, the environmental impacts of CNC preparation at lab (LAB) and industrial (IND) scales were assessed based on the eFootprint system and data from the Chinese Life Cycle Database (CLCD). At the LAB scale, the global warming potential (GWP) reached 3410 kg CO2 eq/kg CNC. The contributions of the U2 (pulp making), U3 (periodate oxidation), U5 (concentration), and U6 (freeze-drying) unit processes were 42.9%, 22.8%, 21.3%, and 10.6%, respectively. At the IND scale, the GWP was reduced by one order of magnitude to 141 kg CO2 eq/kg CNC, and most of the other 13 category indicators of environmental impact (acidification, eutrophication, ecotoxicity, human toxicity, etc.) also showed the same trend. The contribution of the unit process U5 exceeded 50% in the 12 environmental impact indicators. The large contribution of U5 was attributable to the extensive use of ethanol. At the industrial scale, the GWP was reduced to 22.7 kg CO2 eq/kg CNC when the periodate was recycled, and an ultrafiltration membrane system was used to concentrate CNC solutions. The environmental impact of CNC prepared by SPCO was lower than that of CNC prepared by sulfuric acid hydrolysis. This study comprehensively assessed the potential environmental impacts of CNC production on an industrial scale and provided valuable data for future industrial-scale production of CNC and for comparison with alternative products.

Chitin quantitation (as glucosamine) in food raw materials by HPLC[sbnd]C18-DAD with off-line derivatization

This HPLC method is suitable for chitin quantitation (reported as glucosamine) in food raw materials like insects (mealworm larvae, crickets), shrimps, mushrooms and fungi in a research (non-routine) laboratory using a C18 column with HPLC system <600 bar with UV detection capability (at 265 nm). To remove interferences, the sample is defatted (Soxhlet) and deproteinized (by alkali) prior to acid hydrolysis in 6 M HCl. A five-point linear calibration (5–100 µg/mL) is used. The use of fluorescence detection (λex = 260 nm, λem = 350 nm) is also possible with this method [1].•18 min HPLC run time•LOD = 0.05 µg/mL and LOQ = 5 µg/mL

Cellulose nanocrystals as an innovative superdisintegrant for oral dispersible tablets

Oral Dispersible Tablets (ODTs), designed for rapid disintegration in the oral cavity, offer advantages such as easy administration for diverse populations and faster drug absorption. Microcrystalline cellulose (MCC) has been a traditional choice as a disintegrant, but its limitations have led to increased interest in cellulose nanocrystals (CNCs). This study focuses on obtaining and characterizing CNCs derived from MCC by sulfuric acid hydrolysis, exploring different times and drying methods (lyophilization or spray drying). At a 50 % v/v acid concentration for 60 min at 45 °C it was possible to extract CNC with a 76 % yield. When lyophilized, CNC micrographs showed large aggregates with few isolated particles, while the spray-dried samples were seen as free, elongated particles. The resulting CNCs, with enhanced properties like high hydrophilicity and surface area, are investigated for their impact on ODT formulations. All of them disintegrated faster than 10 s. A comprehensive analysis of ODTs' disintegration mechanism was also undertaken. The drying method dictates the predominant disintegration mechanism, even though this is also influenced by the nanoparticle size. Therefore, the study contributes insights into the potential of CNCs as innovative superdisintegrants, offering a promising path for improving oral drug delivery systems.

Exploration and Improvement of Acid Hydrolysis Conditions for Inulin-Type Fructans Monosaccharide Composition Analysis: Monosaccharide Recovery and By-Product Identification.

Acid hydrolysis serves as the primary method for determining the monosaccharide composition of polysaccharides. However, inappropriate acid hydrolysis conditions may catalyze the breakdown of monosaccharides such as fructans (Fru), generating non-sugar by-products that affect the accuracy of monosaccharide composition analysis. In this study, we determined the monosaccharide recovery rate and non-sugar by-product formation of inulin-type fructan (ITF) and Fru under varied acid hydrolysis conditions using HPAEC-PAD and UPLC-Triple-TOF/MS, respectively. The results revealed significant variations in the recovery rate of Fru within ITF under different hydrolysis conditions, while glucose remained relatively stable. Optimal hydrolysis conditions for achieving a relatively high monosaccharide recovery rate for ITF entailed 80 °C, 2 h, and 1 M sulfuric acid. Furthermore, we validated the stability of Fru during acid hydrolysis. The results indicated that Fru experienced significant degradation with an increasing temperature and acid concentration, with a pronounced decrease observed when the temperature exceeds 100 °C or the H2SO4 concentration surpasses 2 M. Finally, three common by-products associated with Fru degradation, namely 5-hydroxymethyl-2-furaldehyde, 5-methyl-2-furaldehyde, and furfural, were identified in both Fru and ITF hydrolysis processes. These findings revealed that the degradation of Fru under acidic conditions was a vital factor leading to inaccuracies in determining the Fru content during ITF monosaccharide analysis.

Efficient production of High-Purity manno-oligosaccharides from guar gum by citric acid and enzymatic hydrolysis

Currently, the production of manno-oligosaccharides (MOS) from guar gum faces challenges of low oligosaccharide enzymatic hydrolysis yield and complicated steps in separation and purification. In this work, a potential strategy to address these issues was explored. By combining citric acid pretreatment (300 mM, 130 °C, 1 h) with β-mannanase hydrolysis, an impressive MOS yield of 61.8 % from guar gum (10 %, w/v) was achieved. The key success lay in the optimizing conditions that completely degraded other galactomannans into monosaccharides, which could be easily removable through Saccharomyces cerevisiae fermentation (without additional nutrients). Following ion exchange chromatography for desalination, and concluding with spray drying, 4.57 g of solid MOS with a purity of 90 % was obtained from 10 g of guar gum. This method offers a streamlined and effective pathway for obtaining high-yield and high-purity MOS from guar gum by combining citric acid pretreatment and enzymatic hydrolysis.

Textile waste subjected to acid hydrolysis as raw materials for biogas production

Textile waste is a high-volume group of municipal waste that is difficult to dispose of due to synthetic additives and chemicals that give natural fibers the properties preferred by consumers. The paper presents a method of treating textile waste based on natural fibers (cotton and wool) with mineral acids and further biological conversion of obtained hydrolysates into biogas. It was found that the hydrolysates of cotton contain a pool of sugars (≥8 g/L of glucose), which are necessary for the growth of microorganism's consortium. The hydrolysates of the mixture of natural and synthetic fibers do not contain fermentation inhibitors (even when cotton was dotted with polyesters and polyamides), and the addition of an appropriate number of wool hydrolysates (up to 5 % v/v) favours the production of biogas. The results indicate that a moderate methane production from waste textiles composed of both cotton and synthetic materials can be achieved with no need of separation, which would significantly increase the cost of their processing.

Optimization of hydrolysis conditions of alginate based on high performance liquid chromatography

Alginate is the most abundant polysaccharide compound in brown algae, which is widely used in various fields. At present, the determination of the content of alginate is mostly carried out using sulfuric acid and trifluoroacetic acid hydrolysis followed by the determination of the content, but the results are not satisfactory, and there are problems such as low hydrolysis degree and low recovery rate. Therefore, in this study, based on the optimization of high performance liquid chromatographic conditions for pre-column derivatization of 1-phenyl-3-methyl-5-pyrazolone (PMP), the hydrolysis effects of sulfuric acid, trifluoroacetic acid (TFA), oxalic acid, and formic acid were compared and the hydrolysis conditions were optimized. The results showed that formic acid was the best hydrolyzing acid. The optimal hydrolysis conditions were 95 % formic acid at 110 °C for 10 h. The hydrolysis effect was stable, with high recovery and low destruction of monosaccharides, which made it possible to introduce formic acid into the subsequent polysaccharide hydrolysis. The pre-column derivatization high performance liquid chromatography method established in this study was accurate and reliable, and the hydrolysis acid with better effect was screened, which provided a theoretical basis for the subsequent determination of alginate content.

Bacterial cellulose nanocrystals obtained through enzymatic and acidic routes: A comparative study of their main properties and in vitro biological responses

Cellulose nanocrystals (CNCs) are crystalline domains isolated from cellulosic fibers. They have been utilized in a wide range of applications, such as reinforcing fillers, antibacterial agents and manufacturing of biosensors. Whitin this context, the aim of this work was to obtain and analyze CNCs extracted from bacterial nanocellulose (BNC) using two distinct methods combined with milling pre-treatment: an acidic hydrolysis using 64 % sulfuric acid and an enzymatic hydrolysis using a commercial cellulase enzyme mixture. The CNCs obtained from the enzymatic route (e-CNCs) were observed to be spherical nanoparticles with diameter of 56 ± 11 nm. In contrast, the CNCs from the acid hydrolysis (a-CNCs) appeared as needle-shaped nanoparticles with a high aspect ratio with lengths/widths of 158 ± 64 nm/11 ± 2 nm. The surface zeta potential (ZP) of the a-CNCs was −30,8 mV, whereas the e-CNCs has a potential of +2.70 ± 3.32 mV, indicating that a-CNCs consisted of negatively charged particles with higher stability in solution. Although the acidic route resulted in nanocrystals with a slightly higher crystallinity index compared to the enzymatic route, e-CNCs was found to be more thermally stable than BNC and a-CNCs. Here, we also confirmed the safety of a-CNCs and e-CNCs using L929 cell line. Lastly, this article describes two different CNCs synthesis approaches that leads to the formation of nanoparticles with different dimensions, morphology and unique physicochemical properties. To the best of our knowledge, this is the first study to yield spherical nanoparticles as a result of BNC enzymatic treatment.

Potencial Citric Acid Production by Fungi Using Hemicellulosic Hydrolysate of Coffee Husk as Substrate

Objective: The aim of this experimental assay was to produce citric acid via submerged fermentation, using hemicellulose hydrolysate from coffee husks as main substrate. Theoretical framework: Obtaining citric acid through fermentation processes, especially submerged fermentation, has become viable due to the use of low-cost materials, such as industrial subproducts derived from green biomass. Methodology: The hemicellulose hydrolysate was obtained from the acid hydrolysis process of the coffee husk. The strains of the fungi Aspergillus niger, Aspergillus westerdijkiae and Rhizopus sp. were employed to carry out the fermentation assays. A bioreactor consisting of a 500 ml flat-bottomed flask was used, with an inlet for supplying air and an outlet for removing samples Results and Conclusion: The obtained results showed an increase in number of spores of the studied fungi as well as citric acid accumulation during the first 72 h of fermentation. On the other hand, after 96 h of fermentation citric acid concentration began to decrease indicating its consumption by the studied fungi, probably due to the lack of nitrogen sources and the cellular stress caused by the mixed composition of the hemicellulose hydrolysate. Implications of the research: There is a need to study the interaction between the nitrogenous nutrients to be added to the fermentation medium and the concentration of reducing sugars as the sole carbon source in the lignocellulosic hydrolysate. Originality/value: This work highlights the potential production of citric acid by fungi using a coffee husk as a renewable biomass.

Coconut fibre for the synthesis of microfibrillated cellulose: Thermal analysis experimental characterization

AbstractFibrillated cellulose at nano‐ and microscales was obtained from green coconut fibre. The biomass was subjected to mechanical treatment (comminution and sieving of the fibres) and chemical treatment (washed with water, treated with sodium hydroxide, bleached with sodium chlorite, and subjected to acid hydrolysis). Finally, purification steps included centrifugation, dialysis, and ultrasound. The product obtained by acid hydrolysis, the crude fibre, and the intermediate‐treated samples were examined by scanning electron microscopy (SEM) and characterized by chemical analysis and thermogravimetry (TGA/DTG). The chemical characterization for crude coconut fibre demonstrated 27.99% ± 1.98% for cellulose, 14.11% ± 4.44% for hemicellulose, 25.15% ± 0.04% for lignin, and 19.34% ± 0.02% for ashes. The applied pretreatment used to remove hemicellulose and lignin from the crude coconut fibre permitted obtaining high levels of cellulose, such as 94.94% ± 5.46% for the hardest condition, with NaOH 11% (w/v)/NaClO2. Then, acid hydrolysis was used to obtain the micro‐scale cellulose structures with 50% H2SO4 at 45°C for 90 min in an agitated condition (100 rpm). Following pretreatment with 2% and 11% NaOH/NaClO2, respectively, microfibrillated cellulose was verified at levels of 0.9% and 0.75% by thermogravimetric analysis, while the commercial sample had a verification level of 1.89%. The produced micro cellulose was fibrillated with a diameter equal to 149.39 ± 40.63 nm and a length of 1764.07 ± 1109.18 nm, as determined by SEM.