Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
Browse
68 results
Search Results
Article Citation - WoS: 2Citation - Scopus: 2Enhanced Reducing Sugar Production and Extraction for Chlorella Vulgaris in Mixotrophic Cultivation Using High Hydrostatic Pressure Processing and Ultrasound(Taylor & Francis, 2023) Uzuner, Sibel; Kurhan, Şebnem; Akdemir Evrendilek, GülsünAlthough extraction of polysaccharides to convert reducing sugars (RS) from microalgae by acid or alkali pretreatments and enzymatic hydrolysis has been extensively studied, few reports exploring the use of high hydrostatic pressure processing (HHP) and ultrasonication (US) as emerging technologies for the extraction of sugars from microalgae biomass exist. Thus, the present study was conducted to determine the effects of mixotrophic growth and stress conditions (NaNO3 and CO2 concentration and light intensity) on RS and protein accumulation in the unicellular green alga Chlorella vulgaris in addition to optimization of the effectiveness of the sequential applications of HHP and US with dilute acid as well as simultaneous enzymatic saccharification on the production of RS from microalga cells. High light intensity, high CO2 concentration and limited nitrogen concentration promoted RS production. The maximum protein content (0.0683 mg g(-1)) was achieved at 0.3 g l(-1) NaNO3 concentration, 7000 mu mol photons m(-2) s(-1) and 6 l min(-1) CO2 concentration. The highest RS content of C. vulgaris after 48 h enzymatic saccharification (583.86 +/- 13.23 mg g(-1)) was obtained at 1% (w/w) acid concentration and 80% amplitude for 30 min with 79.4% RS yield. Combined US-assisted dilute acid pretreatment and enzymatic hydrolysis were also found to be more effective than HHP assisted dilute acid pretreatment and enzymatic saccharification. Therefore, microalgal biomass can be considered a suitable renewable feedstock used in fermentation. Highlights center dot The cultivation period of Chlorella vulgaris was reduced from 25 days to 14 days using mixotrophic growing conditions.center dot Mixotrophic conditions enhanced reducing sugar productivity.center dot Novel extraction techniques enhanced the extraction of reducing sugar from microalgae.Article Enhanced Production of 3-Phenyllactic Acid From Novel Non-Axenic Coculture: Adaptive Evolution and Statistical Fermentation Studies(Springer Heidelberg, 2024) Meruvu, HarithaThis research pivots around screening of idoneous lactic acid bacteria (LAB) from cow milk and subjecting them to adaptive evolution experiments to aid superior growth/robustness necessary for 3-phenyllactic acid (3-PLA) production. Conventional and statistical fermentation studies were conducted at batch scale using a non-axenic coculture of three novel LAB strains: Lactiplantibacillus plantarum str. nov. plantharim, Lactobacillus delbrueckki str. nov. delharim, and Pediococcus pentasaceous str. nov. pentharim. Statistically optimized fermentation using Box Behnken technique resulted in 1225 mg/L 3-PLA production using the growth medium: cheese whey-MRS medium mixture (5:2 ratio), phenylalanine (2.69% w/v), and glucose (9.6% w/v). Statistical optimization of fermentation parameters resulted in a substantial increase (17 times higher) compared to the non-optimized fermentation conditions (72 mg/L). Monad growth kinetics of the cow milk whey (CMW) coculture were calculated and estimated as: mu(max)=0.336 h(-1), K-s=11.64 mg/mL, Y-x/s=0.835 mg/g, Y-P/S=1.66 mg/g, Y-X/P=0.112 mg/mg. The purified 3-PLA (1.93 mg/mL) showed antimicrobial activity with pathogenic bacteria like Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, with a minimum inhibitory concentration of 12 mg/mL.Review Citation - WoS: 25Citation - Scopus: 27Bacillus Cereus: a Review of “fried Rice Syndrome” Causative Agents(Academic Press, 2023) Leong, Sui Sien; King, Jie Hung; Korel, Figen“Fried rice syndrome” originated from the first exposure to a fried rice dish contaminated with Bacillus cereus. This review compiles available data on the prevalence of B. cereus outbreak cases that occurred between 1984 and 2019. The outcome of B. cereus illness varies dramatically depending on the pathogenic strain encounter and the host's immune system. B. cereus causes a self-limiting, diarrheal illness caused by heat-resistant enterotoxin proteins, and an emetic illness caused by the deadly toxin named cereulide. The toxins together with their extrinsic factors are discussed. The possibility of more contamination of B. cereus in protein-rich food has also been shown. Therefore, the aim of this review is to summarize the available data, focusing mainly on B. cereus physiology as the causative agent for “fried rice syndrome.” This review emphasizes the prevalence of B. cereus in starchy food contamination and outbreak cases reported, the virulence of both enterotoxins and emetic toxins produced, and the possibility of contaminated in protein-rich food. The impact of emetic or enterotoxin-producing B. cereus on public health cannot be neglected. Thus, it is essential to constantly monitor for B. cereus contamination during food handling and hygiene practices for food product preparation. © 2023 Elsevier LtdArticle Citation - WoS: 11Citation - Scopus: 10Molecular Evolution and Population Genetics of Glutamate Decarboxylase Acid Resistance Pathway in Lactic Acid Bacteria(Frontiers Media S.A., 2023) Sezgin, Efe; Tekin, BurcuGlutamate decarboxylase (GAD) pathway (GDP) is a major acid resistance mechanism enabling microorganisms’ survival in low pH environments. We aimed to study the molecular evolution and population genetics of GDP in Lactic Acid Bacteria (LAB) to understand evolutionary processes shaping adaptation to acidic environments comparing species where the GDP genes are organized in an operon structure (Levilactobacillus brevis) versus lack of an operon structure (Lactiplantibacillus plantarum). Within species molecular population genetic analyses of GDP genes in L. brevis and L. plantarum sampled from diverse fermented food and other environments showed abundant synonymous and non-synonymous nucleotide diversity, mostly driven by low frequency changes, distributed throughout the coding regions for all genes in both species. GAD genes showed higher level of replacement polymorphism compared to transporter genes (gadC and YjeM) for both species, and GAD genes that are outside of an operon structure showed even higher level of replacement polymorphism. Population genetic tests suggest negative selection against replacement changes in all genes. Molecular structure and amino acid characteristics analyses showed that in none of the GDP genes replacement changes alter 3D structure or charge distribution supporting negative selection against non-conservative amino acid changes. Phylogenetic and between species divergence analyses suggested adaptive protein evolution on GDP genes comparing phylogenetically distant species, but conservative evolution comparing closely related species. GDP genes within an operon structure showed slower molecular evolution and higher conservation. All GAD and transporter genes showed high codon usage bias in examined LAB species suggesting high expression and utilization of acid resistance genes. Substantial discordances between species, GAD, and transporter gene tree topologies were observed suggesting molecular evolution of GDP genes do not follow speciation events. Distribution of operon structure on the species tree suggested multiple independent gain or loss of operon structure in LABs. In conclusion, GDP genes in LABs exhibit a dynamic molecular evolutionary history shaped by gene loss, gene transfer, negative and positive selection to maintain its active role in acid resistance mechanism, and enable organisms to thrive in acidic environments.Article Citation - WoS: 6Citation - Scopus: 6Organosolv Pretreatment of Corncob for Enzymatic Hydrolysis of Xylan(Springer, 2023) Büyükkileci, Ali Oğuz; Temelli, NuranXylan is a renewable polysaccharide, readily available in agricultural and forestry residues. It can be hydrolyzed to produce xylooligosaccharides (XOS) with prebiotic activity and xylose, a precursor for several industrial chemicals. Enzymatic hydrolysis of xylan in the lignocellulosic biomass to obtain xylose and XOS requires a pretreatment to facilitate xylanase activity. In this study, organosolv was evaluated for the delignification of corncob while retaining xylan in the pretreated biomass. The treatment at 170 °C for 1 h with 70% ethanol provided 50% lignin removal and 81% xylan recovery. Increasing temperatures and decreasing ethanol fractions decreased the pH and the xylan recovery. Loss of xylan in the organosolv at 190 °C and in the liquid hot water treatment could be prevented by the addition of 100 mM MgO, without compromising lignin removal. Pretreated corncob was suspended in citrate buffer and hydrolyzed by commercial xylanases. Accellerase XY (250 U/ml) at pH 5.5 and 55 °C and Econase XT (0.6 U/ml) at pH 6.0 and 70 °C provided around 65% xylan digestibility and generated xylose (9.8 g/l) and XOS (10.9 g/l), respectively. This approach could decrease xylan loss and degradation in the pretreatment step and yield clear hydrolysates composed of essentially xylose or XOS. Lignocellulosic biorefineries can benefit from the efficient utilization of xylan, increasing sustainability. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Article Citation - WoS: 2Citation - Scopus: 2Diverse Selection Pressures Shaping the Genetic Architecture of Behçet Disease Susceptibility(Frontiers Media S.A., 2022) Sezgin, Efe; Kaplan, ElifBehçet disease (BD) is a polygenic, multifactorial, multisystem inflammatory condition with unknown etiology. Global distribution of BD is geographically structured, highest prevalence observed among East Asian, Middle Eastern, and Mediterranean populations. Although adaptive selection on a few BD susceptibility loci is speculated, a thorough evolutionary analysis on the genetic architecture of BD is lacking. We aimed to understand whether increased BD risk in the human populations with high prevalence is due to past selection on BD associated genes. We performed population genetics analyses with East Asian (high BD prevalence), European (low/very low BD prevalence), and African (very low/no BD prevalence) populations. Comparison of ancestral and derived alleles’ frequencies versus their reported susceptible or protective effect on BD showed both derived and ancestral alleles are associated with increased BD risk. Variants showing higher risk to and more significant association with BD had smaller allele frequency differences, and showed less population differentiation compared to variants that showed smaller risk and less significant association with BD. Results suggest BD alleles are not unique to East Asians but are also found in other world populations at appreciable frequencies, and argue against selection favoring these variants only in populations with high BD prevalence. BD associated gene analyses showed similar evolutionary histories driven by neutral processes for many genes or balancing selection for HLA (Human Leukocyte Antigen) genes in all three populations studied. However, nucleotide diversity in several HLA region genes was much higher in East Asians suggesting selection for high nucleotide and haplotype diversity in East Asians. Recent selective sweep for genes involved in antigen recognition, peptide processing, immune and cellular differentiation regulation was observed only in East Asians. We conclude that the evolutionary processes shaping the genetic diversity in BD risk genes are diverse, and elucidating the underlying specific selection mechanisms is complex. Several of the genes examined in this study are risk factors (such as ERAP1, IL23R, HLA-G) for other inflammatory diseases. Thus, our conclusions are not only limited to BD but may have broader implications for other inflammatory diseases.Article Citation - WoS: 22Citation - Scopus: 27Layer-By Assembly of Lysozyme With Iota-Carrageenan and Gum Arabic for Surface Modification of Food Packaging Materials With Improved Barrier Properties(Elsevier, 2022) Koca, Nazan; Bayramoğlu, BesteThe study aimed to investigate the surface modification of biaxially oriented polypropylene (BOPP) by layer-by-layer (LbL) assembly of lysozyme (LZ) with two different polysaccharides, iota-carrageenan (IC) and gum arabic (GA), for food packaging applications. The effects of solution pH, adsorption time, elimination of intermediate drying steps were investigated. The LbL film growth was monitored up to 10 deposition steps by UV–Vis spectroscopy and in situ surface plasmon resonance (SPR). The most successful processing conditions for both types of coatings were pH 7–7 combination with intermediate drying and 20 min adsorption time. SPR pointed out a ‘dissolution/reconstruction’ mechanism in film formation. The thickness and surface morphology of the coatings were characterized by Atomic force microscopy (AFM). The surface roughnesses of LZ/IC coatings were higher than that of LZ/GA coatings indicating a denser matrix in the latter. Deposition of 5 bilayers of LZ/IC and LZ/GA on BOPP resulted in 66.15% and 56.89% reduction in oxygen transmission rate (OTR) of the film, respectively. The corresponding reductions in water vapor transmission rate (WVTR) were 28% and 33.52%, respectively. Elimination of intermediate drying steps resulted in less overall deposition, rougher surfaces, diminished oxygen and water barrier properties. The edible LbL coatings obtained in this study possess good gas barrier properties, which is very promising for their use in the preservation of fresh/fresh-cut produce in combination with modified atmosphere packaging applications. The results promise reduced use of plastic films in food packaging.Article Citation - WoS: 11Citation - Scopus: 11Molecular Dynamics Simulations of Duodenal Self Assembly in the Presence of Different Fatty Acids(Elsevier, 2022) Tunçer, Esra; Bayramoğlu, BesteA comprehensive understanding of dietary mixed micelle formation in the presence of lipid digestion products is crucial for an effective design of nutraceutical delivery systems. This study aimed to investigate the duodenal self-assembly of bile lipids and fatty acids (FA) with different characteristics via coarse-grained molecular dynamics (MD) simulations. The results show that increase in FA chain length and unsaturation degree lead to micelles with lower/higher fractions of FAs/bile salts (BS), lower core and surface packing densities, decreased ordering of lipid tails, thus more fluid internal structures. Our findings provide molecular insight into the instability of intestinal colloidal structures composed of long unsaturated FAs. We show the correlation between FA unsaturation degree and lipid packing density is a significant factor in determining the intermicellar BS concentrations. Overall, this study advances the knowledge in the field by establishing a more integral relationship between the FA characteristics and micelle structural properties over a wider range of FA types through MD simulations.Article Citation - WoS: 7Citation - Scopus: 7Effect of Process Parameters and Microparticle Addition on Polygalacturonase Activity and Fungal Morphology of Aspergillus Sojae(Springer, 2022) Germeç, Mustafa; Karahalil, Ercan; Yatmaz, Ercan; Tarı, CananIn this study, the effects of process parameters (initial glucose concentrations, inoculation rates, and nitrogen sources including yeast extract, beef extract, and ammonium nitrate instead of peptone) on polygalacturonase production by Aspergillus sojae in the shaking incubator were examined. Subsequently, the effect of talcum microparticles on activity and morphology was investigated. Based on the results, the highest activity and lowest pellet diameter were 41.91 U/mL and 1411.9 µm when initial glucose concentration and inoculation size were 20 g/L and 12% (v/v), respectively. Besides, as inoculation rate increased, maximum specific growth rate and saturation constant decreased from 0.39 to 0.27 day−1 and 21.26 to 3.50 g/L, respectively. It was determined that highest activity and lowest pellet diameter were found as 18.53 U/mL and 2953.0 µm when medium was supplemented with 2.5 g/L yeast extract. It was also found that as yeast extract and beef extract concentrations increased, pellet diameter decreased. Additionally, medium was supplemented with talcum as a microparticle (0–25 g/L), and maximum activity was 26.59 U/mL (pellet diameter was 2756.3 µm) when talcum concentration was 5 g/L. In addition, as talcum concentration increases from 0.1 to 5 g/L, the biomass concentration increased relatively, but the enzyme activity increased significantly. However, although talcum concentration in the medium is increased until 20 g/L, while the biomass concentration increased, the activity decreased. Compared to control fermentation (without talcum), the activity increased ninefold. Polygalacturonase was also partially purified via ultrafiltration with the purification fold of 1.84. Consequently, fungal morphology in submerged fermentation can be controlled by microparticle addition fermentation, and thus the enzyme activity can be increased.Article Citation - WoS: 17Citation - Scopus: 18Incorporation of Organic Acids Turns Classically Brittle Zein Films Into Flexible Antimicrobial Packaging Materials(Wiley, 2021) Sözbilen, Gözde Seval; Çavdaroğlu, Elif; Yemenicioğlu, AhmetThis study aimed to turn classically brittle zein films into flexible antimicrobial ones by the use of lactic (LA), malic (MA) and tartaric acids (TA). The most effective plasticizer was LA (400% elongation at break [EB] at 4%), while MA (189% EB at 4.5%) and TA (68% EB at 5%) showed moderate and limited plasticizing effects, respectively. The LA- and MA-loaded films maintained their flexibility during 30-day storage at 4 degrees C or 25 degrees C. Fourier transform infrared (FTIR) analysis suggested that the plasticization of LA and MA could be related to secondary structural changes in zein such as increased alpha-helix and random coils (mainly by MA) and spaced/modified intermolecular (only by LA) and intramolecular (mainly by MA) beta-sheets. Atomic force and scanning electron microscopy showed that LA and MA gave more homogenous and smoother films than TA. Films with LA showed the highest water vapour permeability followed by those of control, MA- and TA-loaded films. Films with 3%-4% LA or MA formed clear zones on Listeria innocua and Klebsiella pneumonia, but only films with LA formed clear zones on Escherichia coli. All OA-loaded films gave unclear zones on Staphylococcus aureus in disc-diffusion tests, but this bacterium was inactivated rapidly in antimicrobial tests based on surface inoculation tests. LA is the best OA to develop flexible antimicrobial films from zein, an industrial by-product that films could not have been utilized as a widespread packaging material due to their brittleness.