Comparative study on composition and functional properties of brewer's spent grain proteins precipitated by citric acid and hydrochloric acid

Brewer's spent grain (BSG) is an abundant agro-industrial residue and a sustainable low-cost source for extracting proteins. The composition and functionality of BSG protein concentrates are affected by extraction conditions. This study examined the use of citric acid (CA) and HCl to precipitate BSG proteins. The resultant protein concentrates were compared in terms of their composition and functional properties. The BSG protein concentrate precipitated by CA had 10% lower protein content, 5.8% higher carbohydrate, and 5.4% higher lipid content than the sample precipitated by HCl. Hydrophilic/hydrophobic protein and saturated/unsaturated fatty acid ratios increased by 16.9% and 26.5% respectively, in the sample precipitated by CA. The formation of CA-cross-linkages was verified using shotgun proteomics and Fourier transform infrared spectroscopy. Precipitation by CA adversely affected protein solubility and emulsifying properties, while improving foaming properties. This study provides insights into the role of precipitants in modulating the properties of protein concentrates.

Efficient recovery and characterization of humic acids from municipal and manure composts: A comparative study

The recovery of humic acids from low-quality compost obtained in municipal solid waste treatment plants provides opportunities for its valorization. This study compares the recovery and properties of the humic acids obtained from municipal mixed waste compost (MMWC) and manure compost. The effects of temperature, time, and KOH concentration on the ratio of humic acids in the extracted liquid and the content of organic carbon of the precipitates were investigated by response surface methodology. Optimal conditions were 30 °C and 24 h for both composts, with a KOH concentration of 0.53 M for MMWC and 0.25 M for manure compost. The manure compost provided a liquid extract richer in humic acids than MMWC (76.6 % vs. 33.7 %), but the precipitates presented similar organic carbon contents (38.1 % vs. 42.4 %). Regarding composition, both humic acids presented higher organic carbon and nitrogen contents than the composts used as feedstock. The extraction and further precipitation of humic acids reduced the concentration of heavy metals. Humic acids from manure compost have a slightly higher average molecular weight (2650 Da) than those from MMWC (1980 Da), while both present similar C/N ratios and degree of aromaticity. Most contaminants of emerging concern present in the original composts were not detected in the humic acids. Thus, it was demonstrated that MMWC constitutes an attractive source of humic acids with properties similar to those obtained from a high-quality compost and, therefore, with potential economic value.

Partial characterization of canola (Brassica napus L.) protein isolates as affected by extraction and purification methods

Canola (Brassica napus L.) meal represents a prominent alternative plant-based source for protein isolation. This work aimed to investigate the combined effect of extraction and purification methods for the production of canola protein isolates (CPIs). CPIs were characterized in terms of process yield, protein recovery, basic composition, amino acid profile, in vitro protein digestibility, techno-functional properties, structural properties, and molecular features. The results showed that the Alk-Uf method enhanced yield (16.23 %) and protein recovery (34.88 %). Meanwhile, the Et-Alk-Uf method exhibited the highest crude protein (89.71 %) and free amino nitrogen (4.34 mg g protein-1) contents. Furthermore, protein digestibility (95.5 %) and protein digestibility corrected amino acid score (1.0) were improved using the Et-Alk-Ac method. Conversely, the amino acid composition, secondary structure, and electrophoretic profiles were generally similar for all CPIs. The Alk-Uf and Et-Alk-Uf methods produced isolates with the highest water solubility (∼39.18 %), water absorption capacity (∼3.86 g water g protein-1), oil absorption capacity (∼2.77 g oil g protein-1), and foaming capacity (∼505.26 %). Finally, the foaming stability (93.75 %) and foaming density (34.38 %) were increased when employing the Alk-Ac method. These findings suggest that, in general, the Alk-Uf and Et-Alk-Uf methods can be used to obtain CPIs with high added value for use in food formulations.

Bioaccumulation of titanium dioxide nanoparticles in green (Ulva sp.) and red (Palmaria palmata) seaweed

A bioaccumulation study in red (Palmaria palmata) and green (Ulva sp.) seaweed has been carried out after exposure to different concentrations of citrate-coated titanium dioxide nanoparticles (5 and 25 nm) for 28 days. The concentration of total titanium and the number and size of accumulated nanoparticles in the seaweeds has been determined throughout the study by inductively coupled plasma mass spectrometry (ICP-MS) and single particle-ICP-MS (SP-ICP-MS), respectively. Ammonia was used as a reaction gas to minimize the effect of the interferences in the 48Ti determination by ICP-MS. Titanium concentrations measured in Ulva sp. were higher than those found in Palmaria palmata for the same exposure conditions. The maximum concentration of titanium (61.96 ± 15.49 μg g-1) was found in Ulva sp. after 28 days of exposure to 1.0 mg L-1 of 5 nm TiO2NPs. The concentration and sizes of TiO2NPs determined by SP-ICP-MS in alkaline seaweed extracts were similar for both seaweeds exposed to 5 and 25 nm TiO2NPs, which indicates that probably the element is accumulated in Ulva sp. mainly as ionic titanium or nanoparticles smaller than the limit of detection in size (27 nm). The implementation of TiO2NPs in Ulva sp. was confirmed by electron microscopy (TEM/STEM) in combination with energy dispersive X-Ray analysis (EDX).

Chemical extraction and its effect on the properties of cordleaf burbark (Triumfetta cordifolia A. rich) fibres for the manufacture of textile yarns

Tropical Triumfetta cordifolia (TC) fibre extracted from the equatorial region of Cameroon has been characterized as a potential fibre for textiles. An investigation of extraction parameters to soften this fibre is crucial to use it as a biobased material in the spinning process. To obtain textile quality fibres, 34 sodium hydroxide extraction tests were carried out to study the effect of extraction conditions on its characteristics. Thus, three levels of concentrations (0.5, 1.0 and 1.5 wt%), temperatures (80, 100 and 120 °C) and durations (120, 180 and 240min) were used for extraction by cooking, and at room temperature, durations of 120, 150 or 180 min with three concentrations (2.5, 3.0 and 3.5 wt%) were considered. Only 6 combinations produced fibres that were clear and soft to the touch, without defects (corrugations, stuck fibres) and without residual bark epidermis at the macroscopic scale. For these fibres, the dissolution of non-cellulosic substances, morphological, physical, thermal and mechanical properties depended on the austerity of the alkaline retting. Under mild conditions, the SEM surfaces of the fibres showed large residues of the middle lamella, which made the lignin content (10 wt%) and hydrophilic function higher. Under medium conditions, the fibre surfaces were clean and slightly wrinkled (at 80 °C; 120min). Under severe conditions, heterogeneous transverse shrinkage and wrinkling were observed and accompanied by cellulose degradation (39 wt%) with a significant reduction in tenacity at 16cN/tex. The medium extraction conditions were considered more effective, and their fibres showed cellulose content up to 49 wt%, density up to 1.39 g cm^-3, "Fickian" moisture absorption kinetics with saturation up to 11 wt%, thermal stability up to 237 °C, Young's modulus up to 3.7 GPa, tensile strength up to 113 MPa and tenacity up to 40cN/tex. These new results were compared with lignocellulosic textile fibres in the literature, showing similarity with banana, sisal and jute fibres.

The effect of alkaline extraction and drying techniques on the physicochemical, structural properties and functionality of rice bran protein concentrates

Rice bran protein concentrates (RBPC) were extracted using mild alkaline solvents (pH: 8, 9, 10). The physicochemical, thermal, functional, and structural aspects of freeze-drying (FD) and spray-drying (SD) were compared. FD and SD of RBPC had porous and grooved surfaces, with FD having non-collapsed plates and SD being spherical. Alkaline extraction increases FD's protein concentration and browning, whereas SD inhibits browning. According to amino acid profiling, RBPC-FD9's extraction optimizes and preserves amino acids. A tremendous particle size difference was prominent in FD, thermally stable at a minimal maximum of 92 °C. Increased pH extraction gives FD greater exposal surface hydrophobicity and positively relates to denaturation enthalpy. Mild pH extraction and drying significantly impacted solubility, improved emulsion properties, and foaming properties of RBPC as observed in acidic, neutral, and alkaline environments. RBPC-FD9 and RBPC-SD10 extracts exhibit outstanding foaming and emulsion activity in all pH conditions, respectively. Appropriate drying selection, RBPC-FD or SD potentially employed as foaming/emulsifier agent or meat analog.

Tracking soluble and nanoparticulated titanium released in vivo from metal dental implant debris using (single-particle)-ICP-MS

BACKGROUND

This work studies the presence of the Ti, Al and V metal ions and Ti nanoparticles released from the debris produced by the implantoplasty, a surgical procedure used in the clinic, in rat organs.

METHODS

The sample preparation for total Ti determination was carefully optimized using microsampling inserts to minimize the dilution during the acid attack of the lyophilized tissues by a microwave-assisted acid digestion method. An enzymatic digestion method was optimized and applied to the different tissue samples in order to extract the titanium nanoparticles for the single-particle ICP-MS analysis.

RESULTS

A statistically significant increase was found for Ti concentrations from control to experimental groups for several of the studied tissues, being and particularly significant in the case of brain and spleen. Al and V concentrations were detected in all tissues but they were not different when comparing control and experimental animals, except for V in brain. The possible presence of Ti-containing nanoparticles mobilized from the implantoplasty debris was tested using enzymatic digestions and SP-ICP-MS. The presence of Ti-containing nanoparticles was observed in all the analyzed tissues, however, differences on the Ti mass per particle were found between the blanks and the digested tissue and between control and experimental animals in some organs.

CONCLUSION

The developed methodologies, both for ionic and nanoparticulated metal contents in rat organs, have shown the possible increase in the levels of Ti both as ions and nanoparticles in rats subjected to implantoplasty.

High value-added lignin extracts from sugarcane by-products

This study evaluates the production of lignin bioactive extracts from sugarcane bagasse (SCB) and straw (SCS) alkaline black liquors using greener precipitating agents (methane sulfonic acid (MSA), formic acid (FA) and lactic acid (LA)) as replacers of sulfuric acid (SA), the most common one used in industry. Results showed that the highest precipitation yield was achieved by LA when applied to SCB (14.5 g extract/100 g SCB). Lignin SCB extracts were similar in composition in terms of total carbohydrates (61-70 %), lignin (22-30 %) and inorganics (1.6-2.6 %). Regarding the SCS extracts, similar yields were obtained among all extracts, however, differences in composition were observed between SA and greener precipitating agents, particularly in terms of sugar content. All extracts exhibited radical scavenging activity; overall the extracts were more effective in the scavenging of ABTS radical. FA was the most promising alternative to SA to recover lignin bioactive extracts. This work suggests organic acids as good candidates for obtaining valuable extracts from alkaline pulping of SCB and SCS instead of the conventional sulfuric acid.

Extraction, nutrition, functionality and commercial applications of canola proteins as an underutilized plant protein source for human nutrition

Concerns about sustainability and nutrition security have encouraged the food sector to replace animal proteins in food formulations with underutilized plant protein sources and their co-products. In this scenario, canola protein-rich materials produced after oil extraction, including canola cold-pressed cakes and meals, offer an excellent opportunity, considering their nutritional advantages such as a well-balanced amino acid composition and their potential bioactivity. However, radical differences among major proteins (i.e., cruciferin and napin) in terms of the physicochemical properties, and the presence of a wide array of antinutritional factors in canola, impede the production of a highly pure protein extract with a reasonable extraction yield. In this manuscript, principles regarding the extraction methods applicable for the production of canola protein concentrates and isolates are explored in detail. Alkaline and salt extraction methods are presented as the primary isolation methods, which result in cruciferin-rich and napin-rich isolates with different nutritional and functional properties. Since a harsh alkaline condition would result in an inferior functionality in protein isolates, strategies are recommended to reduce the required solvent alkalinity, including using a combination of salt and alkaline and employing membrane technologies, application of proteases and carbohydrases to facilitate the protein solubilization from biomass, and novel green physical methods, such as ultrasound and microwave treatments. In terms of the commercialization progress, several canola protein products have received a GRAS notification so far, which facilitates their incorporation in food formulations, such as bakery, beverages, salad dressings, meat products and meat analogues, and dairies.

Isolation and characterization of starch from purple yam (Dioscorea trifida)

As a starchy raw material, purple yam presents pigments and mucilaginous material, what can difficult the extraction of pure starch. The extracted starches of Dioscorea trifida by aqueous and alkaline ways were investigated for purity, thermal, physicochemical, technological and functional properties. The starch obtained by alkaline extraction presented higher water absorption capacity and pasting temperature when compared to that obtained by the aqueous extraction method. The starch obtained by the aqueous extraction showed higher oil absorption capacity and less water loss in the freezing-thawing cycles. For both processes, the starches exhibited B-type X-ray diffraction pattern. Thermal analysis showed that both starches pass easily through transition phenomena as observed by T₀ and enthalpy values. The thermal effects presented similar behavior for both extraction methods. Although the extraction method induced changes in the properties of the starches, these changes did not compromise the functionality of the extracted starch and the purple yam starch was left unmodified. Starch can be used in preparations that require higher resistance to high temperatures as well as exposure to longer preparation times.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13197-021-05066-9.

Titanium dioxide nanoparticles assessment in seaweeds by single particle inductively coupled plasma - Mass spectrometry

In this study, a first attempt for isolating and determining (characterising) background levels of titanium dioxide nanoparticles (TiO₂ NPs) in seaweed has been developed by using single particle inductively coupled plasma - mass spectrometry (SP-ICP-MS). Seaweeds were processed using an optimised ultrasound assisted extraction (UAE) procedure based on tetramethylammonium hydroxide (TMAH) before dilution and SP-ICP-MS analysis. The effect of the TMAH percentage in the extracting solution, as well as the volume of extracting solution and sonication (extraction) time, has been fully assessed. Additional experiments also showed that TiO₂ NPs were quantitatively released from the seaweed matrix in one UAE step since the analysis of residues gave TiO₂ NPs concentrations lower than the limit of quantification (LOQ) of the method. Validation of the method with 50 and 100 nm TiO₂ NPs (10 μg L^-1 as Ti) showed good analytical recovery (115% and 112% for 50 and 100 nm TiO₂ NPs, respectively), and good reproducibility (2% for size and 16% for number of TiO₂ NPs). Experiments regarding TiO₂ NPs stability showed that the extracted NPs are stable since there were not changes on the number of TiO₂ NPs and TiO₂ NPs size distributions when exposing TiO₂ NPs standards to the optimised extractive conditions.

Effects of extraction methods on protein properties obtained from paddy rice and germinated paddy rice

Rice protein has attracted considerable attention recently due to its physiological effects. This study extracted the proteins from paddy rice (PR) and germinated paddy rice (GPR) using three methods i.e., alkaline, sodium dodecyl sulfate (SDS) reagent and enzymatic extractions. The extracted proteins or protein fractions were assessed for their properties using various techniques. Data were analyzed by 2'3 factorial design experiment. It was found that germination and extraction methods significantly affected the concentration of protein fractions when analyzed by Bradford assay. Average protein fraction concentration of the GPR was lower than that of PR. SDS-PAGE patterns of protein fractions obtained from PR and GPR using any extraction method displayed similar protein profiles. Three major protein bands at about 13 kDa (prolamin), 22-23 kDa (basic glutelin) and 37-39 kDa (acidic glutelin) with small amount of 57 kDa proglutelin were observed. For amino acid profile, germination increased the content of most amino acids, resulting in the higher content of amino acids in GPR, excepted for some amino acids. When processed with in vitro digestion, protein fractions from GPR exhibited a higher level of digestibility than those from PR as evidenced by the less intensity of the protein bands obtained from SDS-PAGE. Alkaline and SDS reagent extractions provided more digestible protein fractions than enzymatic extraction. Extraction methods also influenced phase transition of protein fractions as investigated by a DSC. Alkaline extraction resulted in protein fractions with higher phase transition temperature than the other methods. For antioxidant capacity, extraction methods as well as germination significantly affected antioxidant capacity of the protein fractions. Enzymatic extraction provided protein fractions with the best antioxidant capacity.

Enzymatic response of ryegrass cellulose and hemicellulose valorization introduced by sequential alkaline extractions

BACKGROUND

In view of the natural resistance of hemicelluloses in lignocellulosic biomass on bioconversion of cellulose into fermentable sugars, alkali extraction is considered as an effective method for gradually fractionating hemicelluloses and increasing the bioconversion efficiency of cellulose. In the present study, sequential alkaline extractions were performed on the delignified ryegrass material to achieve high bioconversion efficiency of cellulose and comprehensively investigated the structural features of hemicellulosic fractions for further applications.

RESULTS

Sequential alkaline extractions removed hemicelluloses from cellulose-rich substrates and degraded part of amorphous cellulose, reducing yields of cellulose-rich substrates from 73.0 to 27.7% and increasing crystallinity indexes from 31.7 to 41.0%. Alkaline extraction enhanced bioconversion of cellulose by removal of hemicelluloses and swelling of cellulose, increasing of enzymatic hydrolysis from 72.3 to 95.3%. In addition, alkaline extraction gradually fractionated hemicelluloses into six fractions, containing arabinoxylans as the main polysaccharides and part of β-glucans. Simultaneously, increasing of alkaline concentration degraded hemicellulosic polysaccharides, which resulted in a decreasing their molecular weights from 67,510 to 50,720 g/mol.

CONCLUSIONS

The present study demonstrated that the sequential alkaline extraction conditions had significant effects on the enzymatic hydrolysis efficiency of cellulose and the investigation of the physicochemical properties of hemicellulose. Overall, the investigation the enzymatic hydrolysis efficiency of cellulose-rich substrates and the structural features of hemicelluloses from ryegrass will provide useful information for the efficient utilization of cellulose and hemicelluloses in biorefineries.

Two-step pretreatment of oil palm trunk for ethanol production by thermotolerent Saccharomyces cerevisiae SC90

Oil palm (Elaeis guineensis) trunk chips were processed by steam explosion under different steam conditions, followed by alkaline extraction and fermentation to produce efficient lignocellulosic ethanol as sustainable alternative energy resource. The optimum condition of steam explosion was attained at 210°C for 4 min (α-cellulose: 58.83% and lignin: 27.12%). Taguchi 3 factor design [(sodium hydroxide concentration (NaOH), temperature and time)] was performed to optimize alkaline extraction. The optimum condition at 15% NaOH, 90°C for 60 min gave highest percentage α-cellulose: 87.14% and lowest percentage of lignin: 6.13%. Simultaneous saccharification and fermentation (SSF) involved 10% dry weight pretreated fibers, Celluclast 1.5L (15 FPU /gram substrate), Novozyme 188 (15 IU/gram substrate) and Saccharomyces cerevisiae SC90. The highest ethanol concentration (C_P) produced during SSF was 44.25 g/L. Nonetheless, pre-hydrolysis simultaneous saccharification and fermentation gave 31.22 g/L (C_P). All results suggested that optimized two step pretreatment produced efficient ethanol.

Comparison of the effectiveness of alkaline and enzymatic extraction and the solubility of proteins extracted from carbohydrate-digested rice

Carbohydrate-digested rice (CDR) residue, the production waste of electrolyte drinks, contains high levels of proteins (approximately 50% of dry matter). Methods for effectively extracting protein from CDR were investigated in this study by comparing alkaline and enzymatic extraction. Alkaline extraction was performed using different concentrations of sodium hydroxide (NaOH). Enzymatic extraction was performed with either commercial Alcalase® or Flavourzyme®. Protein recovery and solubility, and total soluble protein obtained via each method were compared to determine extraction effectiveness. In addition, extraction factors affecting protein recovery were adjusted to determine the optimal conditions for each method. Alcalase provided the maximum protein recovery (30.04%), while less protein recovery was achieved with 0.1 N NaOH (55 °C), 1 N NaOH (55 °C), and Flavourzyme. Although the protein recovery achieved by 0.1 N NaOH (27.43%) was close to that of the Alcalase method, protein solubility by extraction with 0.1 N NaOH was much lower (23.46%) than that achieved via the enzymatic method (100%). Hence, the total soluble protein resulting from Alcalase extraction was higher than that obtained using either of the alkaline methods. Consequently, Alcalase extraction was determined to be the most effective method for extracting protein from CDR.

Enhancing the total organic carbon measurement efficiency for water samples containing suspended solids using alkaline and ultrasonic pretreatment methods

In this study, we investigated the effect of sample pretreatments (ultrasonication and alkaline extraction) on total organic carbon (TOC) measurements for water samples containing suspended solids (SS) of four different origins (algae, soil, sewage sludge, and leaf litter) to more clearly assess the impact of particulate organic carbon (POC) in water. The effects each of ultrasonication (power, pulse, etc.) and alkaline extraction condition (concentration, time, etc.) on the TOC recovery and precision were investigated, and the results were compared with those of a new sample pretreatment method combining both methods. Alkaline treatment (0.01 mol/L NaOH) showed higher precision than ultrasonication (100/5 on/off pulse), and notably, the differences among the measured TOC values in samples of different origins were also further reduced in the alkaline treatment. This suggests that the ultrasonic pretreatment results can be mainly attributed to the increase in POC recovery through particle size reduction, whereas the alkaline treatment results are achieved through the enhancement of POC solubilization. It is also particularly noteworthy that a higher TOC recovery of 87.6% ± 7.4% with a higher precision of 8.4% could be obtained using the combined method, compared to each treatment (ultrasonic: TOC recovery 34.7%, relative standard deviation 63.1%; alkaline: 49.6% and 23.0%, respectively). Thus, simultaneous pretreatment with ultrasonication and alkaline extraction is expected to increase the oxidation rate of organic matter and the homogeneity of the samples, minimizing the loss of POC measurement values, and thereby improving the reliability of the TOC measurements of water samples containing SS.

Solubilization and characterization of extracellular proteins from anammox granular sludge

Elucidating the extracellular polymeric substances (EPS) of anammox granular sludge is important for stable nitrogen removal processes in wastewater treatment. However, due to a lack of standardized methods for extraction and characterization, the composition of anammox granule EPS remains mostly unknown. In this study, alkaline (NaOH) and ionic liquid (IL) extractions were compared in terms of the proteins they extracted from different "Candidatus Brocadia" cultures. We aimed to identify structural proteins and evaluated to which extend these extraction methods bias the outcome of EPS characterization. Extraction was focussed on solubilization of the EPS matrix, and the NaOH and IL extraction recovered on average 20% and 26% of the VSS, respectively. Using two extraction methods targeting different intermolecular interactions increased the possibility of identifying structural extracellular proteins. Of the extracted proteins, ∼40% were common between the extraction methods. The high number of common abundant proteins between the extraction methods, illustrated how extraction biases can be reduced when solubility of the granular sludge is enhanced. Physicochemical analyses of the granules indicated that extracellular structural matrix proteins likely have β-sheet dominated secondary structures. These β-sheet structures were measured in EPS extracted with both methods. The high number of uncharacterized proteins and possible moonlighting proteins confounded identifying structural (i.e. β-sheet dominant) proteins. Nonetheless, new candidates for structural matrix proteins are described. Further current bottlenecks in assigning specific proteins to key extracellular functions in anammox granular sludge are discussed.

Aquatic weeds as novel protein sources: Alkaline extraction of tannin-rich Azolla

The aquatic weed Azolla is a potential protein crop due to its prolific growth and high protein content, supported entirely by nitrogen-fixing symbionts. Alkaline protein extraction at pH 8 followed by acid precipitation allowed recovery of 16-26% of the biomass nitrogen, while at pH 10.5 nitrogen recovery improved to 35-54%. This pH effect was typical of ferns of the family Salviniaceae, and may be explained by high concentrations of condensed tannins (CTs) in the biomass that precipitate protein at mild pH. Two approaches were tested to increase protein yield and reduce protein binding by CTs. Pre-extraction with aqueous acetone (70 v/v%) removed 76-85% of the CTs and subsequent alkaline extraction at pH 12.5 and 95 °C recovered 38% of the biomass nitrogen. Extraction with 1.5% of PEG as a CT-binding agent, also permitted to recover 38% of the nitrogen, under milder conditions of pH 8 and 45 °C.

Characterisation of the in vitro bioactive properties of alkaline and enzyme extracted brewers' spent grain protein hydrolysates

Brewer's spent grain (BSG) is a co-product of the brewing industry that has been shown to contain a range of bioactive peptides encrypted within its protein sequences. Two methods were evaluated herein to generate bioactive peptides; (i) an alkaline extracted BSG protein rich fraction (BSG-PI) was hydrolysed using different combinations of proteolytic enzymes and (ii) BSG was pre-treated with carbohydrases followed by direct hydrolysis using proteolytic enzymes (BSG-DH). BSG-DH with Alcalase/Flavourzyme resulted in significantly higher (p < .05) protein yield when compared to BSG-PI (63.09 ± 0.27 and 58.90 ± 1.45%, respectively). The antioxidant activities (ORAC, FRAP and ABTS) of the BSG-PI and -DH hydrolysates differed depending on the assay and proteolytic enzyme combination preparations used for hydrolysis. Inhibition of DPP-IV by the BSG-PI hydrolysates ranged from 87.01 ± 0.15 to 89.61 ± 0.12% while inhibition by the BSG-DH hydrolysates ranged from 35.71 ± 0.72 to 85.06 ± 0.17%. A significant reduction in the release of interleukin-6 in lipopolysaccharide-stimulated RAW 264.7 cells was observed following treatment with BSG-PI hydrolysates generated with Prolyve/Protease P (58.30 ± 13.76%) and Corolase PP/Flavourzyme (48.02 ± 10.82%) when compared to untreated LPS stimulated control cells (100%). BSG-DH hydrolysates were subjected to in vitro simulated gastrointestinal digestion (SGID) which resulted in a reduction in antioxidant activity, an increase in DPP-IV inhibition and no change in the immunomodulatory activity. Ultrafiltration of selected BSG-DH hydrolysates (through 30 and 10 kDa membranes) gave some permeates with enhanced bioactivities. The results demonstrate that direct enzymatic hydrolysis of BSG is a feasible approach for the generation of bioactive peptides without the prior use of an alkali protein extraction step.

Determination of hexavalent Cr in river sediments by speciated isotope dilution inductively coupled plasma mass spectrometry

During a sampling campaign in September 2015, elevated chromium (Cr) concentrations were observed in sediments of industrially exposed sites of the Sava River (stainless steel production and impact of metallurgic industry). To verify if sediments also contained hazardous hexavalent Cr (Cr(VI)), there was a need to develop a sensitive and reliable analytical procedure for its determination. In the determination of Cr(VI) in environmental samples, it is necessary to evaluate the suitability of the applied analytical methodology for each individual sample matrix. In these studies, the use of isotopically enriched Cr tracers importantly contribute to the validity of the obtained results. In the present work, an analytical procedure was optimised for the extraction of total Cr(VI) from sediments and the content of Cr(VI) determined by high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS). To leach the total amount of Cr(VI) from sediments, an ultrasound-assisted extraction procedure was applied at 80 °C, using 2% NaOH + 3% Na₂CO₃ as the extraction solution. The addition of 0.4 mol L^-1 MgCl₂ prevented oxidation of Cr(III) during the extraction step. To control for species interconversion and for an accurate calculation of Cr(VI) concentration by speciated isotope dilution (ID)-ICP-MS, the alkaline extract was doubly spiked with enriched ⁵⁰Cr(VI) and ⁵³Cr(III). The accuracy of the determination of Cr(VI) was verified by analysing the certified reference material CRM 041 (Cr(VI) in soil), and by spike recovery test. Low limits of detection (LOD) and quantification (LOQ) (1.25 and 4.0 μg Cr(VI) kg^-1, respectively) and good repeatability of measurement (relative standard deviation better than ±4.8%) were obtained. The analytical data revealed that Cr(VI) concentrations in sediments of the Sava River did not represent any known environmental hazard.

Production of bioethanol and value added compounds from wheat straw through combined alkaline/alkaline-peroxide pretreatment

An efficient scheme was developed for the conversion of wheat straw (WS) into bioethanol, silica and lignin. WS was pre-extracted with 0.2 mol/L sodium hydroxide at 30 °C for 5 h to remove about 91% of initial silica. Subsequently, the alkaline-pretreated solids were subjected to alkaline hydrogen peroxide (AHP) pretreatment with 40 mg hydrogen peroxide (H₂O₂)/g biomass at 50 °C for 7 h to prepare highly digestible substrate. The results of enzymatic hydrolysis demonstrated that the sequential alkaline-AHP pretreated WS was efficiently hydrolyzed at 10% (w/v) solids loading using an enzyme dosage of 10 mg protein/g glucan. The total sugar conversion of 92.4% was achieved. Simultaneous saccharification and co-fermentation (SSCF) was applied to produce ethanol from the two-stage pretreated substrate using Saccharomyces cerevisiae SR8u strain. Ethanol with concentration of 31.1 g/L was produced. Through the proposed process, about 86.4% and 54.1% of the initial silica and lignin were recovered, respectively.

Extraction and characterization of proteins from banana (Musa Sapientum L) flower and evaluation of antimicrobial activities

Ultrasonic assisted alkaline extraction of protein from banana flower was optimized using response surface methodology. The extracted proteins were characterized by Fourier transform infrared spectroscopy and molecular weight distribution was determined by gel electrophoresis. The maximum protein yield of 252.25 mg/g was obtained under optimized extraction conditions: temperature 50 °C, 30 min extraction time and 1 M NaOH concentration. The alkaline extraction produced a significantly high protein yield compared to enzymatic extraction of banana flower. Chemical finger printing of proteins showed the presence of tyrosine, tryptophan and amide bonds in extracted protein. Alkaline and pepsin assisted extracted banana flower proteins showed characteristic bands at 40 and 10 kDA, respectively. The extracted proteins showed antibacterial effects against both gram positive and gram negative bacteria. The high protein content and antimicrobial activity indicate the potential applications of banana flower in the food and feed industry.

The effect of non-structural components and lignin on hemicellulose extraction

As the important structural component of corn stover, hemicellulose could be converted into a variety of high value-added products. However, high quality hemicellulose extraction is not an easy issue. The present study aims to investigate the effects of non-structural components (NSCs) and lignin removal on alkaline extraction of hemicellulose. Although NSCs were found to have a minimal effect on hemicellulose dissolution, they affected the color values of the hemicellulose extracts. The lignin limited the hemicellulose dissolution and increased the color value by binding to hemicellulose molecules and forming lignin-carbohydrate complexes. Sodium chlorite method can remove about 90% lignin from corn stover, especially the lignin connected to hemicellulose through p-coumaric and ferulic acids. Which increased the hemicellulose dissolution ratio to 93% and reduced the color value 14-28%, but the cost is about 20% carbohydrates lost.

Selective and cost-effective protocol to separate bioactive triterpene acids from plant matrices using alkalinized ethanol: Application to leaves of Myrtaceae species

Background:

Triterpenes as betulinic (BA), oleanolic (OA) and ursolic acids (UA) have increasingly gained therapeutic relevance due to their wide scope of pharmacological activities. To fit large-scale demands, exploitable sources of these compounds have to be found and simple, cost-effective methods to extract them developed. Leaf material represents the best plant sustainable raw material. To obtain triterpene acid-rich extracts from leaves of Eugenia, Psidium and Syzygium species (Myrtaceae) by directly treating the dry plant material with alkalinized hydrated ethanol. This procedure was adapted from earlier methods to effect depolymerization of the leaf cutin.

Materials and Methods:

Extracts were prepared by shaking the milled dry leaves in freshly prepared 2% NaOH in 95% EtOH solution (1:4 w/v) at room temperature for 6 h. Working up the product in acidic aqueous medium led to clear precipitates in which BA, OA and UA were quantified by gas chromatography.

Results:

Pigment-free and low-polyphenol content extracts (1.2–2.8%) containing 6–50% of total triterpene acids were obtained for the six species assayed. UA (7–20%) predominated in most extracts, but BA preponderated in Eugenia florida (39%). Carried out in parallel, n-hexane defatted leaves led to up to 9% enhancement of total acids in the extracts. The hydroalcoholate treatment of Myrtaceae species dry leaves proved to be a cost-effective and environmentally friendly method to obtain triterpene acids, providing them be resistant to alkaline medium. These combined techniques might be applicable to other plant species and tissues.

Extraction of starch from hulled and hull-less barley with papain and aqueous sodium hydroxide

Starch was isolated from hulled (VJM 201) and hull-less (BL 134) barley with papain and aqueous sodium hydroxide treatments. For enzyme-assisted extraction, barley was steeped in water containing 0.2 % SO2 + 0.55 % lactic acid at 50° ± 2 °C for 4-5 h. The slurry was mixed with 0.4-2.0 g papain/kg barley and incubated at 50° ± 2 °C for 1-5 h. Aqueous sodium hydroxide (0.01-0.05 M) was added to the finely ground barley meal. The alkaline slurry was incubated at ambient temperature (25° ± 2 °C) for 15-60 min. The starch and grain fractions were isolated by screening and centrifugation. Increases in the time of treatment significantly affected the fiber, centrifugation and non-starch residue losses. Concentration of papain and sodium hydroxide had negligible effect on extraction losses. The enzyme-assisted extraction efficiency of starch was higher (80.7-84.6 %) than the alkaline method (70.9-83.7 %). The hulled barley showed higher extraction efficiency than the hull-less barley. The slurry treated with 0.4 g papain/kg barley for 5 h and 0.03 M sodium hydroxide for 60 min produced maximal yield of starch. Barley starch showed desirably high pasting temperature, water binding capacity and hold viscosity; and low final and setback viscosity compared with the commercial corn starch. The alkaline extracted hull-less barley starch showed exceptionally high peak and hold viscosities.