Anti-biofilm activity of marine algae-derived bioactive compounds

A large number of microbial species tend to communicate and produce biofilm which causes numerous microbial infections, antibiotic resistance, and economic problems across different industries. Therefore, advanced anti-biofilms are required with novel attributes and targets, such as quorum sensing communication system. Meanwhile, quorum sensing inhibitors as promising anti-biofilm molecules result in the inhibition of particular phenotype expression blocking of cell-to-cell communication, which would be more acceptable than conventional strategies. Many natural products are identified as anti-biofilm agents from different plants, microorganisms, and marine extracts. Marine algae are promising sources of broadly novel compounds with anti-biofilm activity. Algae extracts and their metabolites such as sulfated polysaccharides (fucoidan), carotenoids (zeaxanthin and lutein), lipid and fatty acids (γ-linolenic acid and linoleic acid), and phlorotannins can inhibit the cell attachment, reduce the cell growth, interfere in quorum sensing pathway by blocking related enzymes, and disrupt extracellular polymeric substances. In this review, the mechanisms of biofilm formation, quorum sensing pathway, and recently identified marine algae natural products as anti-biofilm agents will be discussed.

Enhancing phycocyanin solubility via complexation with fucoidan or κ-carrageenan and improving phycocyanin color stability by encapsulation in alginate-pregelatinized corn starch composite gel beads

Phycocyanin (PC), as a pigment-protein complex, aggregates and precipitates in acidic environments. In this context, complex formation with anionic polysaccharides is a strategy to enhance protein solubility. Besides, acidic conditions negatively affect the inherent blue color of PC, which can be prevented by encapsulation. Thereupon, in the present study, two different biopolymer-based systems, namely complexes and hydrogel beads, were prepared to increase PC solubility and its color stability under acidic conditions, respectively. Fucoidan and κ-carrageenan (KC) were separately utilized to make a complex with PC. Calcium alginate-pregelatinized corn starch (PCS) composite gel beads were used to encapsulate PC. The prepared samples were added into model systems simulating acidic conditions and then characterized during storage at 4 and 25 °C under dark conditions. Appropriate colloidal stabilities were observed for fucoidan/PC and KC/PC model systems. The color of the samples remained stable at 4 °C. As well, the bead carriers (i.e. alginate-PCS) properly protected PC against low pH conditions over time at 4 °C. Thereupon, the blue color of the beads satisfactorily remained stable at this temperature. The findings showed that complexation with fucoidan or KC and encapsulation in mixed hydrogel beads are promising routes for improving PC solubility and its color stability, respectively.

Characterization of the produced electrospun fish gelatin nanofiber containing fucoxanthin

This study aims to prepare fish gelatin nanofibers extracted from fish waste by using electrospinning method and its encapsulation with fucoxanthin extracted from macroalgae Sargassum angustifolium. Four concentrations of gelatin and two concentrations of fucoxanthin were used under different voltage for preparing the nanofibers. The optimal conditions for producing the nanofibers were considered as 30%, 10 cm, 12 kV, and 5% for fish gelatin concentration, distance, voltage, and fucoxanthin, respectively. The average thickness of nanofibers was estimated 198 ± 0.073 nm. The FTIR results confirmed the presence of functional groups between fucoxanthin and gelatin. The loading efficiency of fucoxanthin in nanofibers and the free radical scavenging of DPPH were calculated 91% and 62%, respectively. Further, these nanofibers showed the antibacterial properties against bacteria. Based on the results, the fish gelatin nanofibers containing fucoxanthin can be proposed as a suitable coating for using in the food packaging industry.

Multiple roles of fucoxanthin and astaxanthin against Alzheimer's disease: Their pharmacological potential and therapeutic insights

Alzheimer's disease (AD) is the most devastating neurodegenerative disorder affecting the elderly. The exact pathology of AD is not yet fully understood and several hallmarks such as the deposition of amyloid-β, tau hyperphosphorylation, and neuroinflammation, as well as mitochondrial, metal ions, autophagy, and cholinergic dysfunctions are known as pathologic features of AD. Since no definitive treatment has been proposed to target AD to date, many natural products have shown promising preventive potentials and contributed to slowing down the disease progression. Algae is a promising source of novel bioactive substances known to prevent neurodegenerative disorders including AD. In this context, fucoxanthin and astaxanthin, natural carotenoids abundant in algae, has shown to possess neuroprotective properties through antioxidant, and anti-inflammatory characteristics in modulating the symptoms of AD. Fucoxanthin and astaxanthin exhibit anti-AD activities by inhibition of AChE, BuChE, BACE-1, and MAO, suppression of Aβ accumulation. Also, fucoxanthin and astaxanthin inhibit apoptosis induced by Aβ_1-42 and H₂O₂-induced cytotoxicity, and modulate the antioxidant enzymes (SOD and CAT), through inhibition of the ERK pathway. Moreover, cellular and animal studies on the beneficial effects of fucoxanthin and astaxanthin against AD were also reviewed. The potential role of fucoxanthin and astaxanthin exhibits great efficacy for the management of AD by acting on multiple targets.

Production of an ultrasound-assisted biosurfactant postbiotic from agro-industrial wastes and its activity against Newcastle virus

The objective of this study is to optimize the biosurfactant production by Lactobacillus plantarum ATCC 8014 using low-cost substrates from industrial sources applying ultrasonication at 28 kHz frequency (power of 100 W). Given this, whey permeate and sugar cane molasses were screened to continue optimization using a central composite design to improve the production. Then, the effect of ultrasound was examined at different stages of microbial growth. The combination of whey permeate and sugar cane molasses with yeast extract (2.4 g/L) and inoculum size of 4.8% for 26 h of fermentation time significantly influenced biosurfactant production by reducing the surface tension of water (41.86 ± 0.24 mN/m). Moreover, ultrasonication led to the further reduction in surface tension value (39.95 ± 0.35 mN/m). Further, no significant differences were observed between products from synthetic and waste-based media. The biosurfactants exhibited antiviral activity against Newcastle disease virus (NDV) LaSota strain. It was discovered that biosurfactant produced in agro-food wastes with a significant antiviral effectiveness could be used to develop commercial application instead of chemical surfactants and biosurfactants from expensive synthetic media.

Wheat Germ Fermentation with Saccharomyces cerevisiae and Lactobacillus plantarum: Process Optimization for Enhanced Composition and Antioxidant Properties In Vitro

Wheat germ, a by-product of the flour milling industry, is currently commercialized mainly for animal feed applications. This study aims to explore and optimize the process of wheat germ fermentation to achieve products with enhanced nutritional composition and biological properties and further characterize the fermented products generated using these optimum conditions. The type of microorganism (Saccharomyces cerevisiae 5022 (yeast) and Lactobacillus plantarum strain 299v (bacteria)), pH (4.5, 6, and 7.5) and fermentation time (24, 48, and 72 h) were optimized using response surface methodology (RSM) aiming to achieve fermented products with high total phenol content (TPC), dimethoxy benzoquinone (DMBQ) and antioxidant activities. Optimum fermentation conditions were achieved using L. plantarum, pH 6, 48 h, generating extracts containing TPC (3.33 mg gallic acid equivalents/g), DMBQ (0.56 mg DMBQ/g), and DPPH radical scavenging (86.49%). These optimally fermented products had higher peptide concentrations (607 μg/mL), gamma-aminobutyric acid (GABA) (19,983.88 mg/kg) contents compared to non-fermented or yeast-fermented products. These findings highlight the influence of fermentation conditions of wheat germ and the promising industrial application of wheat germ fermentation for developing food products with enhanced biological properties promising for their commercialization as functional foods.

Combining Knowledge- and Data-Driven Fuzzy Approach to Evaluate Shelf-Life of Various Seafood Products

Due to the complexity of the deterioration process of seafood products, relying on one indicator is not adequate to determine the quality of such products. Usually, shelf-life was estimated based on various indicators complicating the decision-making process. Decision Support Systems are considered as a good solution. The current study aims to establish a simple and novel fuzzy model based on a combination of knowledge- and data-driven approaches to define a fuzzy quality deterioration index (FQDI) in various seafood products (rainbow trout, threadfin bream, and white shrimp samples) during cold storage. Total volatile basic nitrogen (TVB-N) and psychrotrophic microorganisms counts (PMCs) were determined based on traditional methods. The sensory analysis was performed by a data-driven fuzzy approach. Overall, the shelf-life of the rainbow trout fillet was estimated to be 8 days, based on all the freshness parameters. However, the shelf-life of the Japanese threadfin bream fillet was 5–7 days according to the microbial and chemical parameters, respectively. This time for shrimp samples was 6–8 days using sensory score and TVB-N contents. The results of data-driven fuzzy approach showed all of the quality properties were considered as the ‘Important’–‘Very Important’ (defuzzification score >75). The TVB-N and PMCs were the most and weakest freshness quality properties (defuzzified-values: 84.64 and 78.75, respectively). Based on FQDI, the shelf-life of the rainbow trout, Japanese threadfin bream, and shrimp samples were estimated to be 8, 5, and 7 days, respectively. This method was able to successfully provide a comprehensive deterioration index for evaluating the seafood shelf-life. Such a total index can be considered as a comprehensive output (y variable) to predict seafood freshness by rapid and nondestructive method.

Utilization of the human gamma-satellite insulator for the enhancement of anti-PCSK9 monoclonal antibody expression in Chinese hamster ovary cells

Monoclonal antibodies (mAbs) are widely employed as invaluable therapeutics for a vast number of human disorders. Several approaches have been introduced for the improvement of mAb production in Chinese hamster ovary (CHO) cells due to the increasing demand for these products. In this regard, various chromatin-modifying elements such as insulators have been incorporated in the expression vectors to augment mAb expression. In this study, human gamma-satellite insulator containing vectors were utilized for the expression of an anti-proprotein convertase subtilisin/kexin type 9 (PCSK9) mAb in CHO-K1 cells. To this aim, dual expression vectors encoding the antibody light chain (LC) and heavy chain (HC) with or without the insulator element were constructed, and mAb expression was evaluated in transient and stable expression. Based on the results, mAb expression significantly increased in the stable cell pool, and clonal cells developed using the human gamma-satellite insulator. In contrast, transient antibody expression was not affected by the insulator element. Finally, the enhancement of LC and HC mRNA levels was found in the insulator containing stable cell pools using the quantitative real-time-polymerase chain reaction (qRT-PCR). Our findings showed the positive effect of the human gamma-satellite insulator on the stable expression of an anti-PCSK9 immunoglobulin G1 (IgG1) mAb in CHO-K1 cells using dual expression vectors.

Structure-function engineering of novel fish gelatin-derived multifunctional peptides using high-resolution peptidomics and bioinformatics

The multifunctional properties of fish gelatin hydrolysates have not been completely elucidated. Here, the biological characterization of these peptides was performed to engineer multifunctional peptides. Bioactive peptides were produced from mackerel byproducts via successive enzymatic hydrolysis reactions using subtilisin A and actinidin as microbial and herbal proteases. The antibacterial activity against both gram-negative and -positive food-borne pathogens, including Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae, as well as the inhibitory potential of angiotensin-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV), was accessed in vitro. The synthesized peptides demonstrated multifunctional properties, which were further confirmed by in silico protocols. The ACE and DPP-IV inhibitory (IC₅₀) values of P1, P2, and P3 were 0.92 and 0.87, 0.51 and 0.93, 0.78 and 1.16 mg mL⁻¹, respectively. Moreover, the binding energy was sufficient for all three peptides to inhibit both ACE and DPP-IV enzymes with excellent three-dimensional conformation (RMSD = 0.000) for all six docking mechanisms.

Evaluation of the total volatile basic nitrogen (TVB-N) content in fish fillets using hyperspectral imaging coupled with deep learning neural network and meta-analysis

Recently, hyperspectral-imaging (HSI), as a rapid and non-destructive technique, has generated much interest due to its unique potential to monitor food quality and safety. The specific aim of the study is to investigate the potential of the HSI (430-1010 nm) coupled with Linear Deep Neural Network (LDNN) to predict the TVB-N content of rainbow trout fillet during 12 days storage at 4 ± 2 °C. After the acquisition of hyperspectral images, the TVB-N content of fish fillets was obtained by a conventional method (micro-Kjeldahl distillation). To simplify the calibration models, nine optimal wavelengths were selected by the successive projections algorithm. A seven layers LDNN was designed to estimate the TVB-N content of samples. The LDNN model showed acceptable performance for prediction of TVB-N content of fish fillet (R²p = 0.853; RSMEP = 3.159 and RDP = 3.001). The performance of LDNN model was comparable with the results of previous works. Although, the results of the meta-analysis did not show any significant difference between various chemometric models. However, the least-squares support vector machine algorithm showed better prediction results as compared to the other models (RMSEP: 2.63 and R²_p = 0.897). Further studies are required to improve the prediction power of the deep learning model for prediction of rainbow-trout fish quality.

Exploitation of Ultrasound Technique for Enhancement of Microbial Metabolites Production

Microbial metabolites have significant impacts on our lives from providing valuable compounds for nutrition to agriculture and healthcare. Ever-growing demand for these natural compounds has led to the need for smart and efficient production techniques. Ultrasound is a multi-applicable technology widely exploited in a range of industries such as chemical, medical, biotechnological, pharmaceutical, and food processes. Depending on the type of ultrasound employed, it can be used to either monitor or drive fermentation processes. Ultrasonication can improve bioproduct productivity via intensifying the performance of living organisms. Controlled ultrasonication can influence the metabolites' biosynthesis efficiency and growth rates by improvement of cell permeability as well as mass transfer and nutrient uptake rates through cell membranes. This review contains a summarized description about suitable microbial metabolites and the applications of ultrasound technique for enhancement of the production of these metabolites as well as the associated downstream processing.

Antioxidant mechanism, antibacterial activity, and functional characterization of peptide fractions obtained from barred mackerel gelatin with a focus on application in carbonated beverages

The present study aimed to use fish by-products to generate gelatin peptides with potential applications in carbonated beverages. After ultrafiltration, the F < 3 kDa (fraction < 3 kDa) showed the highest peptide concentration (227.22 mg/g) as well as antibacterial (MIC of ≤ 0.5 mg/mL) and antioxidant activities, including hydroxyl and superoxide radical scavenging, ferrous chelation, and ferric reduction (with IC₅₀ values of 0.88, 1.04, 0.50 mg/mL, and 0.58, respectively). 2,2-diphenyl-1-picrylhydrazyl scavenging was the highest in the 3 < F < 10 kDa (IC₅₀ of 0.64 mg/mL). In vitro gastrointestinal digestion significantly decreased all biological activities. Solubility, water holding capacity, and emulsifying activity of the F < 3 kDa were the highest while foaming properties and overfoaming were reversibly related to the molecular weight. All abovementioned properties, in addition to in vitro cytotoxicity analysis in different cell lines and better flavor characteristics, indicated that the F < 3 kDa could be safely and properly used as an ingredient for the fortification of carbonated beverages.

Lactobacillus plantarum-derived biosurfactant: Ultrasound-induced production and characterization

The aim of the present study was to investigate the effect of ultrasonic treatment (25 kHz) on biosurfactant production by Lactobacillus plantarum ATCC 8014. The impacts of the ultrasonication (with a frequency of 25 kHz and power of 7.4 W for 30 min time duration) were examined at different stages of the fermentation process to obtain the optimum stimulation instant(s). The optimum scenario was found to be one-time sonication at the 12^th hour of fermentation which can be beneficial from an economic point of view (compared with multiple applications of sonication). Ultrasonic treatment at this time resulted in enhancement of the productivities of biomass (4.5 g/L) and biosurfactant (2.01 g/L) which was almost 1.3 times higher than those of the non-sonicated control samples. According to our results, it was clearly observed that glucose consumption increased after ultrasonic treatment representing the improved substrate uptake and progression of the cellular metabolism. Furthermore, the transmission electron microscopic images immediately after sonication clarified the pore formation on the cell surfaces. The results also indicated the enhancement of plasma membrane permeability of the sonicated cells. Fourier transform infrared spectroscopy and scanning electron microscopy coupled with energy dispersive x-ray spectroscopy analyses also disclosed respectively no structural differences before and after ultrasonic exposure in the produced biosurfactant and bacterial cell membrane. The biosurfactant was characterized to be a mixture of carbohydrate (28%), protein (23%) and lipid (specified by gas chromatography-mass spectrometry) known as glycolipoprotein. The sustainable critical micelle concentration and the stability of the synthesized biosurfactant can feature its potential applicability in various processes in the food and pharmaceutical industries.

Production of second-generation biodiesel using low-quality date fruits

This study focused on the valorization of the date syrup obtained from low-quality date fruits to be used as a low-cost alternative medium for producing single cell oil (SCO) by Rhodotorula glutinis PTCC5256, which could further be converted into biodiesel. The higher C/N ratio of date syrup (C/N 70) led to restricting the formation of cell biomass and enhancing the biosynthesis of SCO. The maximal cell biomass and lipid productivities were obtained 72 mg/L/h and 17 mg/L/h by C/N ratios of 20 and 70, respectively. Although the obtained biodiesel met the international standards for cold filter plugging point (4.92 °C), iodine value (87.22 g I₂/100 g oil), cetane number (52.26), higher heating value (40.19 MJ/kg), cloud point (6.29 °C), pour point (0.00 °C), density (878 kg/m³), kinematic viscosity (4.30 mm²/s) and oxidation stability (7.87 h), its weak cold-flow properties might limit its application in cold areas in comparison with diesel fuel.

Double encapsulation of fucoxanthin using porous starch through sequential coating modification with maltodextrin and gum Arabic

This study aims to assess the effect of gum Arabic (GA), maltodextrin (MD), or their combination as a coating agent at different ratios (1/3, 1/5, and 1/7 w/w) to encapsulate fucoxanthin. For this purpose, fucoxanthin was initially extracted and purified from Sargassum angustifolium brown seaweed and then loaded into porous starch (PS). The fucoxanthin-loaded PS samples were further contributed in another encapsulation process using the coating materials. All samples were evaluated in terms of encapsulation efficiency, Fourier-transform infrared (FTIR) spectroscopy and stability under light, dark and low or high temperature (4 and 50°C) exposure over a certain time period. Purification of fucoxanthin was verified through HPLC and NMR spectroscopy. It was shown that the subsequent coating with MD + GA (1/7 w/w) caused an enhanced encapsulation of fucoxanthin-loaded PS, reaching to about 96%. In addition, the stability of fucoxanthin-loaded PS was greatly influenced by light and high temperature exposure and decreased from 85% to 58% using the GA-coated material (1/3 w/w). First-order kinetic model was found to be fitted well on thermal degradation data of fucoxanthin. Interestingly, the mixture of MD + GA (1/7 w/w) exhibited the highest fucoxanthin prevention at the end of the storage period. Conclusively, the findings of this study can provide simple and facile protocol for food chemists in protecting the food ingredients using encapsulation process.

Stimulation of biosurfactant production by Lactobacillus plantarum using ultrasound

Due to their nonpathogenic status, biosurfactants produced by Lactobacillus strains have been shown to have potential applicability in several industrial sectors, particularly food and pharmaceutical industries. However, products with high efficiency are needed to fulfill the demand for these biosurfactants. Therefore, the present study investigated kinetic parameters, biomass and biosurfactant production of Lactobacillus plantarum ATCC 8014 applying standard MRS and modified MRS (supplemented standard MRS by nitrogen and carbon sources) culture medium under various ultrasonic frequencies of 20, 25, 35, 45, 130 and 950 kHz to obtain more efficient conditions. The optimum conditions were found when using the modified MRS treated by the frequency of 25 kHz (the power of 7.4 W) for 30 min, which led to a significant effect on the growth rate (µ_max, h^-1) rather than control. Furthermore, this condition caused the highest population (10.07 ± 0.1 log CFU/mL) and biomass concentration (4.33 ± 0.06 g/L), and lowest surface tension (39.26 ± 0.5 mN/m), leading to higher biosurfactant production. Hence, given the results of the present study, it can be established that controlled ultrasound exposure and supplementation of culture media using the main growth factors can intensify the microbial activity and the productivity of biological processes.

Prediction of various freshness indicators in fish fillets by one multispectral imaging system

In current study, a simple multispectral imaging (430–1010 nm) system along with linear and non-linear regressions were used to assess the various fish spoilage indicators during 12 days storage at 4 ± 2 °C. The indicators included Total-Volatile Basic Nitrogen (TVB-N) and Psychrotrophic Plate Count (PPC) and sensory score in fish fillets. immediately, after hyperspectral imaging, the reference values (TVB-N, PPC and sensory score) of samples were obtained by traditional method. To simplify the calibration models, nine optimal wavelengths were selected by genetic algorithm. The prediction performance of various chemometric models including partial least-squares regression (PLSR), multiple-linear regression (MLR), least-squares support vector machine (LS-SVM) and back-propagation artificial neural network (BP-ANN) were compared. All models showed acceptable performance for simultaneous predicting of PPC, TVB-N and sensory score (R²_P ≥ 0.853 and RPD ≥ 2.603). Non-linear models were considered better quantitative model to predict all of three freshness indicators in fish fillets. Among the three spoilage indices, the best predictive power was obtained for PPC value and the weakest one was acquired for TVB-N content prediction. The best model for prediction TVB-N (R²_p = 0.862; RMSEP = 3.542 and RPD = 2.678) and sensory score (R²_p = 0.912; RMSEP = 1.802 and RPD = 3.33) belonged to GA-LS-SVM and for prediction of PPC value was BP-ANN (R²_p = 0.921; RMSEP = 0.504 and RPD = 3.64). Therefore, developing multispectral imaging system based on LS-SVM model seems to be suitable for simultaneous prediction of all three indicators (R²_P > 0.862 and RPD > 2.678). Further studies needed to improve the accuracy and applicability of HSI system for predicting freshness of rainbow-trout fish.

Physicochemical, rheological, and molecular characterization of colloidal gelatin produced from Common carp by-products using microwave and ultrasound-assisted extraction

The effects of ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) methods on molecular and physicochemical characteristics of the resultant gelatin were examined. Before extraction procedure, we investigated the optimum pH for swelling of Common carp by-products, which is an important pretreatment for gelatin production. The highest swelling yield was achieved at pH 13 among pH 1-14 with unit intervals. Results indicated that the UAE gelatin has a higher gel strength, viscosity, melting point, and gelling point. The power and time of sonication showed a reverse relation with these characteristics. In addition, as the time of microwave heating was raised, the gel strength, viscosity, melting point, and gelling point were decreased. The FT-IR spectra showed similar peaks but the Amide B in UAE gelatin slightly vanished. The electrophoretic pattern also revealed the higher gel strength and viscosity of UAE gelatin due to the higher intensity of α and β chains compared to MAE gelatin. It can be concluded from all of the results of this study that the produced gelatin using these procedures can be a good source of gelatin in food and drug industries.

Biosurfactant Production by Lactic Acid Bacterium Pediococcus dextrinicus SHU1593 Grown on Different Carbon Sources: Strain Screening Followed by Product Characterization

The present study focused on producing and characterizing a type of biosurfactant (BS) derived from lactic acid bacteria (LAB) and its potential applications in pharmaceutical and food industries due to the preference of employing nonpathogenic organisms in bioprocesses. To this aim, several screening approaches were applied to identify an efficient BS-producing strain from a set of LAB, and Pediococcus dextrinicus SHU1593 was selected as the most operative one. The BS produced by P. dextrinicus was isolated and structurally characterized as a lipoprotein with an approximately equal ratio of lipids (~52% (w/w)) and proteins (47% (w/w)). It reduced the surface tension (ST) of phosphate-buffered saline (PBS) from 72.80 ± 0.10 to 39.01 ± 0.32 mN/m. The results also indicated the potential of developing low-cost strategies aimed at the production of efficient LAB-derived BSs which are structurally and quantitatively similar to the ones obtained from conventional media. Finally, given the physical and functional characterization (i.e. critical micelle concentration (CMC), emulsification index (%E₂₄), stability, as well as antimicrobial and anti-adhesive activities) of the BS produced in the present study, it can be introduced as a promising candidate to be employed in plenty of areas in pharmaceutical and food industries.

Gelatin production using fish wastes by extracted alkaline protease from Bacillus licheniformis

An effort was made to produce gelatin from Common carp wastes using extracted alkaline protease from Bacillus licheniformis PTCC 1595. Fermentation was performed by submerged media for 48 h and 72 h. The hydrolyzing enzyme was added in 5, 10, 15, 20, and 25 units per gram of wastes powder for hydrolysis. The produced gelatin was compared with commercial bovine gelatin with regard to some rheological and physicochemical properties. The yield of gelatin production was also determined as a result of hydroxyproline extraction from fish wastes. SDS-PAGE was performed for enzyme and gelatins. For enzyme, two bands were achieved with 39 and 10.5 kDa molecular weight which were separated passing through a 15 kDa UF filter. Both gelatins showed β, α₁, and α₂ chains as basic components, but the fish waste gelatin showed narrow bands. In conclusion, foam expansion and water holding capacity were approximately equal in both gelatin types used for food industry application. The results indicated that using 20 units of enzyme per gram of waste powder was the optimum amount of enzyme application. Further, fish wastes were concluded to be a practical source for gelatin production.

Enhanced biosurfactant production with low-quality date syrup by Lactobacillus rhamnosus using a fed-batch fermentation

Novel strategies toward the use of low-cost media to produce food-grade microbial products have been considerably attended in recent years. In this study, date syrup obtained from low-quality date fruits was implemented for biosurfactant production by the probiotic bacterium, Lactobacillus rhamnosus PTCC 1637. The most level of biosurfactant was achieved through fermentation in a bioreactor with a lactose feeding phase, up to 24 h. Critical micelle concentration of the cell-bound biosurfactant was found to be 6.0 mg/ml with a minimum surface tension value of 39.00 mN/m and a maximum emulsifying index of 42%. The spectrum of Fourier transform infrared spectroscopy taken from the cell-bound biosurfactant suggests that it should be a multi-component mixture of protein and polysaccharides associated with phosphate groups. The results indicated the potential for developing strategies toward the low-cost production of food-grade biomaterials by probiotic microorganisms.

The inhibitory potential of Zataria multiflora and Syzygium aromaticum essential oil on growth and aflatoxin production by Aspergillus flavus in culture media and Iranian white cheese

Antifungal activity of essential oils (EOs) of Zataria multiflora (thyme) and Syzygium aromaticum (clove) against Aspergillus flavus growth and aflatoxin B₁ production was studied in potato dextrose agar (PDA) and potato dextrose broth (PDB), as well as in Iranian white cheese as a food model. The results showed that the inhibitory potential of EOs in the PDB medium is more than PDA medium. Clove EO on PDB medium prevented fungal growth and aflatoxin B₁ production at 300 and 100 ppm, respectively. However, the thyme EO was not able to inhibit fungal growth completely and showed the strongest inhibition effect at 400 ppm. EOs also had more inhibitory activity in laboratory culture media than the food environments. EOs in all concentrations reduced aflatoxin B₁ production and fungal growth in cheese, but only the clove EO at 150 ppm was able to prevent the fungal growth and aflatoxin B₁ production completely. Thyme EO reduced aflatoxin B₁ value to below detection threshold (2 ppb) at 10 μl. Our findings propose EOs as a natural inhibitor to control fungal contamination of foodstuffs such as Iranian white cheese.

Biodegradable Chitosan Coating Incorporated with Black Pepper Essential Oil for Shelf Life Extension of Common Carp (Cyprinus carpio) during Refrigerated Storage

Chitosan (Ch) coating incorporated with black pepper essential oil (Ch+BPEO) was studied to extend the shelf life of common carp (Cyprinus carpio) during refrigerated storage at 4 ± 1°C. The chemical composition of BPEO was characterized using gas chromatography-mass spectrometry (GC-MS). Antibacterial properties of BPEO were determined by disk diffusion agar, MIC, and MBC. Ch (2% [wt/vol]) and Ch+BPEO (2% [wt/vol] Ch with 1.5% [vol/vol] BPEO) were used for common carp fillet coating. The samples were analyzed periodically for chemical (pH, total volatile basic nitrogen) and microbiological (aerobic plate count, psychrophilic bacteria count, lactic acid bacteria, and Enterobacteriaceae bacterial counts) characteristics during 16 days. The GC-MS results indicated that main components in BPEO were carene, caryophyllene, limonene, β-pinene, and α-pinene. The samples coated with Ch and Ch+BPEO resulted in lower pH and total volatile basic nitrogen values in comparison with the control. The microbiological analysis of fish fillets during refrigerated storage clearly indicated that Ch+BPEO coating significantly reduced the fish fillet microbial load. The aerobic plate count, psychrophilic bacteria count, lactic acid bacteria count, and Enterobacteriaceae bacterial count of samples coated with Ch+BPEO were reduced approximately 4.1, 3.9, 2.3, and 2.8 log CFU/g, respectively, at the end of the storage period. Finally, Ch and Ch+BPEO effectively improved the quality of fish fillet during refrigerated storage and extended the shelf life of fish fillets from 8 to 16 days.

KEY WORDS

Black pepper; Chitosan; Common carp; Essential oil.

Influence of extraction methods on antioxidant and antimicrobial properties of essential oil from Thymua danesis subsp. Lancifolius

The essential oil (EO) from dried ground powder leaves and stems of Thymua danesis was extracted using hydrodistillation (HD), ohmic extraction (OE), ultrasound‐assisted HD and ultrasound‐assisted OE methods. Then, the antioxidant, antimicrobial, and sensory properties of the EO were investigated both in vitro and in food systems. Thyme EO extracted by ultrasound‐assisted HD method had promising antibacterial activities against Escherichia coli and Staphylococcus aureus and had the best antioxidant properties when tested in vitro. In food systems, higher concentrations of the EO were needed to exert similar antibacterial and antioxidant effects. Furthermore, thyme EO added yogurt and drink yogurt revealed better sensory properties than the control and fresh samples. Essential oil from Thymua danesis has a good potential to be used as an antioxidant, antimicrobial, and flavoring agent in food systems and the extraction method effects on the antioxidant and antimicrobial properties of the thyme extract.

Optimization of processing conditions to improve antioxidant activities of apple juice and whey based novel beverage fermented by kefir grains

A central composite design (CCD) was used to evaluate the effects of fermentation temperature (20-30 ºC) and kefir grains amount (2-8%w/v) on total phenolic content and antioxidant activities of apple juice and whey based novel beverage fermented by kefir grains. The response surface methodology (RSM) showed that the significant second-order polynomial regression equation with high R(2) (>0.86) was successfully fitted for all response as function of independent variable. The overall optimum region was found to be at the combined level of 7.56%w/v kefir grains and temperature of 24.82 ºC with the highest value for total phenolic content (TPC) and antioxidant activities. At this optimum point TPC, 1, 1-Diphenyl-2-picrylhydrazyl radical scavenging, metal chelating effect, reducing power, inhibition of linoleic acid autoxidation and inhibition of ascorbate autoxidation were 165.02 mgGA/l, 0.38 ml/1 ml, 0.757 (absorbance at 700 nm), 46.12 %, 65.33 % and 21 %, respectively. No significant difference (p < 0.05) was found between actual values and predicated values.

The Effect of Microwave Pasteurization on Some Physical and Chemical Characteristics of Milk

In this research, cow’s milk was pasteurized using microwave (MW) or HTST methods and their effects on some milk components were studied. The results showed no differences between some physico-chemical characteristics like protein, fat, acidity, and solubility percentages due to heat treatments with either MW or HTST and the control samples. The contents of six amino acids (aspartic acid, glycine, glutamic acid, histidine, arginine, and lysine in mg/L) and fatty acids (weight percentage) showed no significant differences using either MW or HTST pasteurization method. There were slight but insignificant differences in trans fatty acid and D-amino acid contents in the milk pasteurized with either MW or HTST method. SDS-PAGE and HPLC analysis of milk proteins did not reveal any differences between the pasteurization methods. It was finally concluded that MW heating is a good alternative to HTST pasteurization.