Furfural Levels Research Articles

Automated yeast cultivation control using a biosensor and flow cytometry.

Effective microbial bioprocessing relies on maintaining ideal cultivation conditions, highlighting the necessity for tools that monitor and regulate cellular performance and robustness. This study evaluates a fed-batch cultivation control system based on at-line flow cytometry monitoring of intact yeast cells having a fluorescent transcription factor-based redox biosensor. Specifically, the biosensor assesses the response of an industrial xylose-fermenting Saccharomyces cerevisiae strain carrying the TRX2p-yEGFP biosensor for NADPH/NADP+ ratio imbalance when exposed to furfural. The developed control system successfully detected biosensor output and automatically adjusted furfural feed rate, ensuring physiological fitness at high furfural levels. Moreover, the single-cell measurements enabled the monitoring of subpopulation dynamics, enhancing control precision over traditional methods. The presented automated control system highlights the potential of combining biosensors and flow cytometry for robust microbial cultivations by leveraging intracellular properties as control inputs.

Quality characteristics of goat milk powder produced by freeze drying followed by UV-C radiation sterilization

Goat milk was directly freeze-dried into milk powder after freezing and then sterilized using UV-C radiation to produce low-dose, medium-dose and high-dose UV-C radiation sterilized freeze-dried goat milk powder (LGP, MGP and HGP). UV-C sterilization effectively reduced the total bacteria count and coliform bacteria in the goat milk powder while preserving the active proteins, and maintaining the color unchanged. Additionally, LGP, MGP, and HGP all exhibited a moisture content below 5 g/100 g and water activity below 0.5. Upon reconstitution, the milk powder formed uniform and stable emulsion. During accelerated storage tests, the increased Aw did not compromise the microbial quality of milk powder, and there were no significant changes in active proteins as confirmed via SDS-PAGE results. Furthermore, the color parameters (a*, b* and ΔE) showed a strong correlation with hydroxymethyl furfural levels.

An emerging application of gamma irradiation in reducing higher levels of hydroxymethyl furfural (toxic hazard) in date syrup and enhancing the microbial and nutritional quality.

Date syrup is a very rich nutritional and medicinal product. It can be used alone or mixed with other food products. Now, it is widely used as a natural sweetener instead of harmful sugar in several food products. However, date syrup contains higher levels of 5-hydroxyl methyl furfural (5-HMF) (heat-induced toxicant). HMF is normally formed during processing via Maillard reaction as a result of heating. Thus, the present study aims at investigating the effect of gamma irradiation in reducing HMF content and improving the quality properties of date syrup. Date syrup samples (commercial) were irradiated at different doses (15, 20 and 25 kGy). HMF content was determined using the HPLC method. The obtained results showed that γ-irradiation reduced the toxic compound (HMF) in date syrup, where irradiation dose (20 kGy) recorded the lowest HMF level (1956.40 mg/kg) with a reduction percentage of 46.96% compared to the non-irradiated sample. While the non-irradiated sample revealed the highest level of HMF and bacterial growth. Therefore, γ-irradiation is considered an effective treatment that reduces HMF using a particular dose (20 kGy) and prevents microbial growth (20-25 KGy). Furthermore, it may increase the nutritional value by increasing minerals' bioavailability (15 kGy).

Formation and migration of 5-hydroxymethylfurfural and furfural from food contact bamboo sticks during heating and their safety evaluation

Bamboo sticks intended for food contact can produce 5-Hydroxymethylfurfural (5-HMF) and Furfural (FF) when used in high-temperature scenarios (e.g., barbecue and Kanto boil). The influencing factors in terms of baking conditions, salinity, pH, and dipping time of water on the formation of 5-HMF and FF in bamboo sticks were investigated. Specific migration of 5-HMF and FF also have been studied in bamboo sticks in contact with food simulants (water, 10 % ethanol, and 4 % acetic acid). The results showed that the effects of baking temperature and time on the formation of both showed a similar pattern which firstly increased and decreased afterward. Both 5-HMF and FF levels in bamboo sticks increased with decreasing pH and the presence of salt. After dipping bamboo sticks in water for a while, the moisture content of higher than 10 % in bamboo sticks presented low levels of 5-HMF and FF. In the case of all food simulants, the highest migrated concentration of 5-HMF and FF were found in 4 % acetic acid. Since there are no specific migration limits for 5-HMF and FF, estimated daily intake is calculated to evaluate their safety. Based on the studied migration results, 5-HMF and FF in bamboo sticks are relatively safe for consumers.

Evaluating the chemical and metal contamination of commercial Rakı, a grape-based alcoholic beverage from Turkey

Turkish Rakı is one of the most consumed alcoholic beverages in Turkey. The chemical and metal contamination of alcoholic beverages is a threat to human health and lowers the quality of the product. Ethyl carbamate and furfural are carcinogenic to animals, and have been classified as Group 2A and 3 agents respectively by the International Agency for Research on Cancer. Factors, such as raw materials, process time and storage, affect metal concentrations in beverages. Limits for chemicals and metals in Rakı have not yet been established by the Turkish agency. The present study aimed to evaluate the chemical and metal contamination of commercial Turkish Rakı. Thirty-seven different types of Turkish Rakı were purchased from local markets in Turkey. Ethyl carbamate (EC) and furfural (FR) levels were measured by Gas Chromatography-Mass Spectroscopy (GC-MS). Arsenic, copper, lead, and zinc levels were measured by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES). None of the Rakı samples contained EC. Furfural was not detected in commercial Rakı samples but only in illegal Rakı samples. Ethanol and methanol levels complied with Turkish regulation. Our data shows that commercial Rakı from Turkey was contaminated by very low amounts of arsenic (<LOD–0.02 mg/L), copper (0.05–0.41 mg/L), lead (< LOD–0.03 mg/L) and zinc (0.01–0.39 mg/L).

Direct electrochemical determination of very low levels of 5-hydroxymethyl furfural in natural honey by cyclic and square wave voltammetric techniques

The present study reported the electrochemical determination of 5-hydroxymethylfurfural (HMF) obtained by the degradation of fructose, with a glassy carbon electrode. This study was performed by cyclic voltammetry (CV) and square wave voltammetry (SWV). The aim of this work was to propose a direct and rapid technique to quantify HMF in honey. The effect of scan rate, pH and temperature was evaluated to select the optimum experimental conditions. HMF was irreversibly reduced, thus producing a single cathodic peak at a potential of −1.6 V vsSCE in the presence of Na2SO4 as supporting electrolyte involving a transfer of two electrons. The diffusion coefficient was calculated from convoluted cyclic voltammograms and was found to be 2.23 10−6 cm2 s−1. The voltammetric determination of HMF was carried out under optimum conditions. The calibration curves for the determination of HMF exhibited the good linear responses within the concentration range from 0.15 to 1.26 mg L−1 for CV method and from 0.03 mg L−1 to 0.38 mg L−1 for SWV method. In water, the quantification limits of HMF were about 83.3 10−3 mg L−1 and 7.2 10−3 mg L−1 for CV and SWV, respectively. The SWV technique showed a higher sensitivity and reproducibility in analytical response. In honey solution, the limit of quantification was found to be 0.02 mg L−1. The method was successfully applied to the analysis of HMF in honey and syrup samples containing different concentrations with good recovery values.

Valorisation of sawdust through the combined microwave-assisted hydrothermal pre-treatment and fermentation using an oleaginous yeast

Oleaginous yeast, cultured on second-generation lignocellulosic resources, has the potential to be a key part of the future energy sector. However, the multiple unit operations necessary to produce concentrated hydrolysates, with a minimum of fermentation inhibitors, limit the applicability to date. In this study, a simple microwave-assisted hydrothermal pre-treatment step of oak or beech sawdust was deployed to produce an oligosaccharide-rich hydrolysate. This was then catabolised by the oleaginous yeast, Metschnikowia pulcherrima, avoiding the need for costly enzymatic or further chemical steps in the processing. Up to 85% of the sawdust’s hemicelluloses could be solubilised under these conditions, and 8 g/L DCW yeast with a 42% lipid content produced. While a number of studies have demonstrated that oleaginous yeasts possess high inhibitor tolerance, using this real lignocellulosic hydrolysate, we demonstrate that lipid production is actually very sensitive to inhibitor and carbon availability, and the optimal system is not the one that gives the highest hydrolysate or cell biomass. Indeed, the yeast was shown to detoxify the inhibitors in the process, but at high inhibitor loading, this leads to very poor lipid production, especially at high furfural levels. These findings clearly highlight the importance of considering multiple variables when real, complex lignocellulosic media are involved, tuning process conditions based on the desired fermentation outcomes.

Effect of furfural addition on validamycin-A production in fermentation of Streptomyces hygroscopicus 5008

Furfural is one of main inhibitors in hemicellulose hydrolysates such as xylose mother liquor, but its positive effect on the production of validamycin-A (VAL-A), a widely used agricultural antibiotic, was interestingly found in fermentation of Streptomyces hygroscopicus 5008. The furfural level in medium up to 1 g/L was effectively converted to furfuryl alcohol and furoic acid by the microorganism. Both intracellular H2O2 level and ValG enzyme activity of the cells were enhanced by furfural addition. Xylose mother liquor medium with supplementation of about 1 g/L furfural could enhance the VAL-A titer by 39 %. This work is helpful to VAL-A fermentation using the hemicellulose hydrolysate.

Effect of Dilute-acid Hydrolysis Conditions on Sugar and Productions from Paragrass

In this study, the productions of sugars as well as inhibitory compounds, e.g hydroxymethylfurfural (HMF) and furfural, from paragrass (Brachiaria mutica) were investigated using dilute acid hydrolysis. Sulphuric acid concentration of 1.0, 1.2, 1.5 and 2.0 wt% and reaction temperature of 120, 130, 140 and 150 °C for either 30 or 60 min were investigated. Xylose was found to be the major product at a maximum yield of 99±3 mg/g grass using 1.2 wt% H2SO4 and reaction temperature of 140 °C for 30 min. Analysis of variance (ANOVA) showed that for the reaction temperature between 120-140 °C, sulphuric acid concentration was the most important factor affecting the yields of hemicellulose sugars from paragrass. However, the temperature ≥ 150 °C caused the marked drop in all sugar compounds. At the optimal condition, the concentration of HMF was 0.16 g/l and furfural 0.09 g/l. The formation of HMF and furfural was almost linearly increased with increasing hydrolysis temperature between 120 and 150 °C. Furthermore, longer reaction times led to higher levels of HMF and furfural. The dilute acid hydrolysis in series with enzyme saccharification of paragrass yielded 122 mg total reducing sugar (TRS) per g grass in the enzyme hydrolysate.

Development and Validation of UV-Visible Spectrophotometric Method for the Determination of 5-Hydroxymethyl Furfural Content in Canned Malt Drinks and Fruit Juices in Ghana

A simple, rapid, accurate, and less expensive spectrophotometric method has been developed for the quantitation of 5-hydroxymethyl furfural (5-HMF) levels in canned malt drinks and fruit juice drinks sampled in the Kumasi Metropolis, Ghana. The quantitation is based on the selective maximum absorption of ultraviolet radiation by 5-HMF at the wavelength (λmax) of 284 nm using acetonitrile : water (50 : 50 v/v) as the solvent system. The method was established to be specific, precise, and accurate over a concentration range of 0.001 mg/ml–0.02 mg/ml. 5-HMF levels in fruit juice samples (A1–A10) were between 0.132 mg/ml and 0.438 mg/ml, and these levels were shown to be comparable (t = 2.200;p=0.0553) to the contents in the canned malt samples (M1–M10) which were between 0.3140 mg/ml and 0.7170 mg/ml. The study failed to show any dependence of 5-HMF levels on the composition of the product as well as the manufacturing process adopted. The length of storage did also not significantly affect the 5-HMF levels in the products.

Ethanol fermentation from non-detoxified lignocellulose hydrolysate by a multi-stress tolerant yeast Candida glycerinogenes mutant

The aim of this work was to study ethanol fermentation properties of the robust mutant Candida glycerinogenes UG21 from non-detoxified lignocellulose hydrolysate. C. glycerinogenes UG21 with high tolerance to elevated temperature, acetic acid, and furfural was obtained and applied in lignocellulose-based ethanol production. C. glycerinogenes UG21 exhibited highly-efficient degradation ability to furfural. High levels of acetic acid and furfural inhibited cell growths and ethanol production of Saccharomyces cerevisiae ZWA46 and industrial Angel yeast but had a slight impact on biomass and ethanol titer of C. glycerinogenes UG21. Using non-detoxified sugarcane bagasse hydrolysate, C. glycerinogenes UG21 reached 1.24 g/L/h of ethanol productivity at 40 °C but ethanol production of S. cerevisiae ZWA46 and Angel yeast was inhibited. Further, C. glycerinogenes UG-21 exhibited 2.42-fold and 1.58-fold higher productivity than S. cerevisiae ZWA46 and Angel yeast under low-toxicity hydrolysate. Therefore, C. glycerinogenes UG-21 could be an excellent candidate for low-cost lignocelluloses ethanol production.

Carbonyl compounds in different stages of vinification and exposure risk assessment through Merlot wine consumption

ABSTRACTThe objective of this research was to estimate for the first time the transformations that the free form of some target carbonyl compounds may undergo during winemaking and assess the exposure risk to these compounds through the consumption of the Merlot commercial wines under study. Acrolein and furfural were found in grapes and the respective wines, although levels were observed to decline throughout the winemaking process. Formaldehyde was found in all stages of wine production in levels lower than the limit of quantification of the method and ethyl carbamate was not found in samples. Acetaldehyde seems to be a precursor of acetoin and 2,3-butanediol, since the levels of this aldehyde decreased along winemaking and the formation of the ester and alcohol was verified. Furfural levels decreased, while the occurrence of furan-containing compounds increased during winemaking. The formation of acetaldehyde during alcoholic fermentation and the potential environmental contamination of grapes with acrolein and furfural are considered as the critical points related to the presence of toxic carbonyl compounds in the wine. Acrolein was found in the samples under study in sufficient quantities to present risk to human health, while other potentially toxic carbonyl compounds did not result in risk. This study indicated for the first time the presence of acrolein in grapes suggesting that environmental pollution can play an important role in the levels of this aldehyde detected in wines. Reduction of the emission of this aldehyde to the environment may be achieved by replacing wood burning by another heat source in fireplaces or wood stones, and abandoning the practice of burning garbage and vegetation.

Comparison of ethanol yield from pretreated lignocellulo-starch biomass under fed-batch SHF or SSF modes

The ethanol yields from lignocellulo-starch biomass (peels of sweet potato, elephant foot yam, tannia, greater yam and beet root) by fed-batch separate hydrolysis and fermentation (F-SHF) and simultaneous saccharification and fermentation (F-SSF) using Saccharomyces cerevisiae were compared. Fed-batch saccharification of steam or dilute sulphuric acid pretreated biomass enhanced the reducing sugar yield which resulted in high RS consumption, volumetric ethanol productivity and ethanol yield during the first 24 h fermentation under F-SHF mode, while continuous production and utilization of reducing sugars occurred up to 72 h in F-SSF. Dilute sulphuric acid pretreated residues under F-SHF gave higher ethanol yield (34–43 g/L) and productivity (274–346 ml/kg dry biomass) than steam pretreatment (27–36 g/L and 223–295 ml/kg respectively), while F-SSF was superior for steam pretreated peels of sweet potato, elephant foot yam and tannia giving ethanol yields from 281 to 302 ml/kg. Glucose and xylose were present in all the hydrolysates with a preponderance of glucose and fermentation resulted in significant reduction in glucose levels in both F-SHF and F-SSF. Higher levels of total soluble phenolics and hydroxymethyl furfural were observed in the hydrolysates from dilute sulphuric acid pretreatment and yeast assimilated/detoxified part of the inhibitors, while only trivial amounts of furfural were present due to the low xylose content in the hydrolysates. Continuous formation led to higher accumulation of inhibitors in F-SSF despite supplementation with the detoxification mix comprising Tween 20, polyethylene glycol and sodium borohydride. F-SHF of dilute sulphuric acid pretreated biomass could be considered as a comparatively advantageous process where only one time feeding of enzyme cocktail and yeast was adopted compared to multiple feeds of enzymes and yeast along with other additives such as detoxification mix or nutrient solution in F-SSF.

Furfural-tolerant Zymomonas mobilis derived from error-prone PCR-based whole genome shuffling and their tolerant mechanism.

Furfural-tolerant strain is essential for the fermentative production of biofuels or chemicals from lignocellulosic biomass. In this study, Zymomonas mobilis CP4 was for the first time subjected to error-prone PCR-based whole genome shuffling, and the resulting mutants F211 and F27 that could tolerate 3g/L furfural were obtained. The mutant F211 under various furfural stress conditions could rapidly grow when the furfural concentration reduced to 1g/L. Meanwhile, the two mutants also showed higher tolerance to high concentration of glucose than the control strain CP4. Genome resequencing revealed that the F211 and F27 had 12 and 13 single-nucleotide polymorphisms. The activity assay demonstrated that the activity of NADH-dependent furfural reductase in mutant F211 and CP4 was all increased under furfural stress, and the activity peaked earlier in mutant than in control. Also, furfural level in the culture of F211 was also more rapidly decreased. These indicate that the increase in furfural tolerance of the mutants may be resulted from the enhanced NADH-dependent furfural reductase activity during early log phase, which could lead to an accelerated furfural detoxification process in mutants. In all, we obtained Z. mobilis mutants with enhanced furfural and high concentration of glucose tolerance, and provided valuable clues for the mechanism of furfural tolerance and strain development.

Production of Fermentable Sugars and a High Protein Meal by Dilute Acid Hydrolysis of Soybean Meal at High Temperatures

The objective was to produce fermentable sugars with low levels of fermentation inhibitors and a high-protein meal, with acceptable color, by treating defatted soybean meal with dilute sulphuric acid at temperatures between 105 and 135 oC and durations up to 45 min. The conditions that maximized the amount of protein were 120 °C, 0.5% H2SO4, and 45 min, which increased protein from 48.1% to 58.6% d.b. The highest amount of fermentable sugars (32.2% d.b.), without regard for the protein content, was for the treatment at 135 °C, 2% H2SO4, and 45 min; such treatment generated relatively low 5-HMF and furfural levels (0.0018 g/L and 0.32 g/L, respectively), and 0.87 g/L, of acetic acid. The treatment at 120 °C, 1.5% H2SO4, and 30 min had the best balance between a high concentration of fermentable sugars (21.3% d.b.) in the liquid fraction and crude protein (52.1% d.b.) in the solid fraction without a significant change in the original color of the solid fraction.

Synthesis of bio-adhesives from soybean flour and furfural: Relationship between furfural level and sodium hydroxide concentration

Soybean–furfural (SoyFu) adhesives were synthesized through cross-linking soybean flour with furfural under alkaline conditions and the performance of the resulting bio-adhesives was evaluated by manufacturing plywood panels. A total of 30 different bio-adhesive formulations were studied (5 levels of furfural content and 6 levels of sodium hydroxide or pH). Thirty 2-ply plywood panels prepared with these adhesives were pressed at 140°C for 4min. Shear tests were performed on the panels according to ASTM D2339-1998 (2004). The statistical analysis indicated that an interaction existed between furfural (crosslinker) and sodium hydroxide (pH) levels. The best quality panels were produced using adhesives containing high levels of sodium hydroxide (12, 20 and 28g/100g soy flour) and high levels of furfural (50 and 100g/100g soy flour). 13C nuclear magnetic resonance analyses were also performed on a selected formulation. The spectra analysis, however, did not prove that furfural was involved in covalent or ionic bonds with soybean flour.

Effects of formulation and extrusion cooking conditions on furfural and hydroxymethylfurfural content

The objective of this research was to investigate the effects of different ingredients (reducing sugars, leavening agents, citric acid), processing conditions (feed moisture content, exit die temperature), and extrusion cooking methods (with/without CO2 injection) on furfural and 5-hydroxymethylfurfural (HMF) formation in corn-based extrudates. The decrease in furfural levels was 16% upon addition of sodium-bicarbonate, while the increase was 12% upon addition of ammonium-bicarbonate for extrudates produced at 150 °C and feed moisture content of 22%. The furfural concentration of extrudates produced at 150 °C and feed moisture content of 22% without leavening agents was 810 μg/100 g and increased to 11,901 μg/100 g upon citric acid addition (about a 15-fold increase). Furthermore, both low feed moisture and high exit die temperature had promoting effects on furfural and HMF contents. The CO2 injection method did not have considerable effect on furfural and HMF levels of the extrudates; however, it positively affected the physical properties of extrudates.

Monitoring of low levels of furfural in power transformer oil with a sensor system based on a POF-MIP platform.

In this work an innovative, miniaturized and low cost optical chemical sensor (POF-MIP platform), based on a molecular imprinted polymer (MIP) and surface plasmon resonance in a plastic optical fiber (POF), is presented and preliminarily tested for monitoring of furfural (furan-2-carbaldehyde) in transformer oil. To this end, the optical platform was coupled to an MIP layer, highly selective for furfural. The ability of the developed sensor to directly detect furfural in the insulating oil was investigated. The detection limit of the sensor has been found to be 9 ppb, with a linear response up to about 30 ppb. However there is a sensible response up to 0.15 ppm. Because of the small linearity range, the Hill equation is suggested for the quantification. The sensor has been effectively tested in real oil samples collected from aged electrical equipment removed from service. The assessed concentration of furfural is in good agreement with that evaluated by a high pressure liquid chromatography (HLPC) method, confirming the good selectivity of the proposed sensor.

Wheat bran biorefinery: an investigation on the starch derived glucose extraction accompanied by pre- and post-treatment steps.

Wheat bran, a side product of the milling industry, can be considered as a feedstock for biorefineries. Unlike other lignocellulosic feedstock, wheat bran contains a reasonable amount of starch, which is not of recalcitrant nature. Therefore, it can be extracted without a costly pretreatment process. The present work evaluates the extraction of starch derived glucose in relation to a wheat bran biorefinery. The purity of free glucose extracted quantitatively was 44%. The extract was concentrated by threefold via nanofiltration, thereby reaching a glucose concentration of 49 g/L. Hydrothermal treatment (180°C - 20 min) of the starch-free bran did not induce the formation of hydroxymethylfurfural and levulinic acid. Interestingly, the furfural level increased compared to the process, in which bran was treated hydrothermally without a preceding starch extraction. By separation of water-extractables prior to enzymatic hydrolysis, the free glucose purity was increased to 58%, however the yield of glucose decreased to 61%.

Assessment of hydroxymethylfurfural and furfural in commercial bakery products

A survey was conducted on the presence of hydroxymethylfurfural (HMF) and furfural in bread and bakery products; for this purpose a reliable extraction procedure followed by high performance liquid chromatography (HPLC) was applied. The performance of the method was evaluated in terms of linearity (r always>0.99); detection limits (0.001mgL−1 for furfural and 0.006mgL−1 for HMF); recovery percentages (98.5–100.5% for HMF and 94.9–98.9% for furfural); intraday precision (<4.65%) and interday precision (<7.51%). Two batches of a wide variety of products commercially available were analysed (a total of 88 samples). HMF and furfural levels presented high variability between products and batches of the same product. Cake/pastry samples showed the lowest HMF content (3.0mgkg−1fw) while biscuits showed the highest content (7.8mgkg−1fw) (p<0.05). Regarding furfural, bread samples presented the highest furfural content (5.3mgkg−1fw) (p<0.05), cake/pastry and biscuits showed the lowest content (1.9 and 3.0mgkg−1fw, respectively). Chocolate containing samples presented higher amounts of furfural (>20mgkg−1). These results indicate that special attention should be given to furfural content of bread (due to its daily high consumption) and re-evaluation of dietary exposure.