Apple pomace ultrafiltration sludge – A novel substrate for fungal bioproduction of citric acid: Optimisation studies

Ever-growing demand for citric acid (CA) and urgent need for alternative sources has served as a driving force for workers to search for novel and economical substrates. Submerged fermentation was conducted using apple (Malus domestica) pomace ultrafiltration sludge as an inexpensive substrate for CA bioproduction, using Aspergillus niger NRRL567. The crucial parameters, such as total suspended solids and inducer concentration, were optimised by response surface methodology for higher CA production. The optimal CA concentrations of 44.9 g/100 g and 37.9 g/100 g dry substrate were obtained with 25 g/l of initial total solids and 3% (v/v) methanol and 25 g/l of total solids and 3% (v/v) ethanol concentration, respectively, after the 144 h of fermentation. Results indicated that total solids concentration, and methanol as an inducer, were effective with respect to higher CA yield and also indicated the possibility of using apple pomace sludge as a potential substrate for economical production of CA.     

Biotechnological potential of industrial wastes for economical citric acid bioproduction by Aspergillus niger through submerged fermentation

Submerged citric acid (CA) bioproduction was carried out by Aspergillus niger NRRL‐567 using various industrial wastes, such as brewery spent liquid (BSL), lactoserum and starch industry water sludge. CA bioproduction was carried out by varying the temperature (25–35 °C), pH (3–5), addition of inducers, incubation time and supplementation with different proportions of apple pomace ultrafiltration sludge (APS). The results indicated that under the best conditions with 3% (v/v) methanol, the optimal concentration of 11.34 g L^?1 CA was recorded using BSL at pH 3.5 and temperature 30 °C after 120‐h incubation period. Supplementation of methanol resulted in an increase of 56% CA production. Meanwhile, under similar conditions, higher concentration of 18.34 g L^?1 CA was reported with the supplementation of BSL with 40% (v/v) APS having suspended solids concentration of 30 g L^?1. The present study demonstrated the potential of BSL supplemented with APS as an alternative cheap substrate for CA fermentation.     

Modelling Milk Lactic Acid Fermentation Using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS)

The purpose of the current work was to investigate the capability of multivariate curve resolution-alternating least squares (MCR-ALS) to extract relevant information from Fourier transform near-infrared (FT-NIR) spectra acquired on-line with a fibre probe during milk lactic acid fermentation. The fermentation trials were conducted replicating twice a factorial design with three different starter cultures (Streptococcus thermophilus and Lactobacillus bulgaricus alone or as 1:1 mixed culture) and three different incubation temperatures (37, 41 and 45 °C), for a total of 18 experiments. The runs were monitored for 7.5 h through pH measurement, dynamic oscillatory test for rheological properties evaluation and FT-NIR spectra acquisition. The obtained MCR-ALS models successfully described the experimental FT-NIR spectra recorded (99.9 % of explained variance, 0.63665 % lack of fit, and standard deviation of the residuals lower than 0.0072). The three spectral profiles obtained by MCR-ALS pointed to the characteristic coagulation phases of milk lactic acid fermentation. The concentration profiles defined as a function of time for each run were strongly dependent on starter and temperature tested, in agreement with pH and rheological results. MCR-ALS applied to FT-NIR spectroscopy provides to the dairy industry a control system which could be implemented in-line as reliable management method for monitoring fermentation processes and to define the coagulation profile no matter the operative conditions adopted for the process.     

Extremely low-frequency magnetic fields affect pigment production of Monascus purpureus in liquid-state fermentation

Red pigment is one of natural coloring agents produced from the secondary metabolites of Monascus purpureus. Measures are taken to increase the pigment production. Effect of the extremely low-frequency magnetic field on the red and yellow pigment production of M. purpureus in liquid-state fermentation was estimated by exposing fermentation broth, medium and sterile distilled water used to prepare medium. The maximum yield of red and yellow pigment production had about 20 and 36 % increase for 8 days at 0.4 mT when treating fermentation broth compared to the control value. For sterile distilled water, a significant increase occurred at 0.4 mT compared to 0.1 mT for 5 h. However, the red and yellow pigment production decreased significantly at magnetic fields of 0.9 and 1.2 mT when treating fermentation broth and sterile distilled water. In contrast, the yield of both red and yellow pigment production decreased significantly compared with the control exposure for 3 and 5 h at a magnetic field of 0.4 mT. Different solution (cellular suspension, medium and sterile distilled water) exposure to magnetic fields has different bioeffect on M. purpureus SKY219. The appropriate magnetic field treatment could increase the efficiency of red and yellow pigment production.     

Characterization of composition,antioxidant potential and microbial organisms upon submerged <Emphasis Type="Italic">Cicer arietinum</Emphasis> fermentation

The aim of this work was to investigate the composition, antioxidant potential and microbial content of chickpea (Cicer arietinum) steep liquor (CSL) during a submerged fermentation. Chickpea seeds (250 g) were soaked in boiled distilled water (1:2, w/v) for 24 h at 37 °C then filtered and freeze-dried to obtain 8.2 g of CSL. Lysine was the main amino acid accounted for 77.0 % of total free amino acids followed by serine (6.49 %). The results of total amino acids found in CSL indicated that arginine was the main amino acid accounted for 24.0 % of total amino acids followed by tyrosine (20.0 %). Total carbohydrate in the freeze-dried CSL was 1.47 %, wherein reducing sugar was 1.25 % of total carbohydrates. Levels of nicotinic acid, pyridoxine, thiamin, riboflavin, folic acid, and vitamin B₁₂ were 14.3, 3.14, 24.2, 1.11, 0.59 and 24.5 mg/100 mg CSL, respectively. CSL exhibited antioxidant activity (AA) wherein AA was increased with increasing the fermentation time. After 24 h of fermentation, AA of CSL reached 77.0 % while tertiary butyl hydroquinone exhibited 82.0 %. Twenty-five Bacilli isolates were separated from freeze-dried CSL on nutrient broth medium. CSL might be used as an alternative to yeast extract for syngas fermentation because it is rich in nutrients and cheaper compared to yeast extract.     

Maximization of Fructooligosaccharides and β-Fructofuranosidase Production by Aspergillus japonicus under Solid-State Fermentation Conditions

The conditions of temperature, moisture content, and inoculum rate able to maximize the production of fructooligosaccharides (FOS) and β-fructofuranosidase (FFase) enzyme by solid-state fermentation were established. Fermentation assays were performed using the support material (coffee silverskin) moistened to 60, 70, or 80 % with a 240-g/l sucrose solution and inoculated with a spore suspension of Aspergillus japonicus to obtain 2?×?10⁵, 2?×?10⁶, or 2?×?10⁷ spores/gram dry material. The fermentation runs were maintained under static conditions at 26, 30, or 34 °C during 20 h. The moisture content did not influence the FOS and FFase production; however, temperature between 26 and 30 °C and inoculum rate of approximately 2?×?10⁷ spores/gram dry material maximized the results (FOS?=?208.8 g/l with productivity of 10.44 g/l h; FFase?=?64.12 units U/ml with productivity of 4.0 U/ml h). These results are considerably higher than those obtained under no optimized fermentation conditions and represent an important contribution for the establishment of a new industrial process for FOS and FFase production.     

Production of 3-phenyllactic acid and 4-hydroxyphenyllactic acid by Pediococcus acidilactici DSM 20284 fermentation

It was reported that 3-phenyllactic acid (PLA) and 4-hydroxyphenyllactic acid (HPLA) could be produced by Pediococcus acidilactici DSM 20284. PLA and HPLA concentrations were 0.65 and 0.25 mM when P. acidilactici DSM 20284 was grown in MRS broth for 36 h. In comparison with P. acidilactici DSM 20284 fermentation using MRS medium alone, PLA and HPLA production could be significantly promoted by the supplement of the corresponding amino acid (phenylalanine and tyrosine) and ketoacid (phenylpyruvic acid and 4-hydroxyphenylpyruvic acid) precursors in MRS broth, but inhibited by the supplement of the non-corresponding precursors. Promotion and inhibitory effects were both strengthened when supplement amounts increased. Ketoacids precursors showed more promotion effect on the corresponding 2-hydroxy acids production than amino acid precursors; however, amino acid precursors showed more inhibitory effect on non-corresponding 2-hydroxy acids production than ketoacids precursors.     

Microbial Production of Citric Acid by Solid State Fermentation of Kiwifruit Peel

A solid-state fermentation method was developed for the production of citric acid from kiwifruit peel by Aspergillus niger NRRL 567. This method produced about 100g citric acid per kg of kiwifruit peel fermented in the presence of 2% methanol at 30°C in 4 days. The yield was more than 60% based on the amount of fermentable sugar consumed.     

Rheological characteristics of vegetable oils as affected by deep frying of French fries

Fatty acid composition and rheological characteristics of sunflower oil (SO), cottonseed oil (CO) and palm olein (PO) during deep frying for 4–16 h were investigated. In the different oils, linoleic acid decreased while palmitic, stearic and oleic acids increased in the bath oil during frying. Total phenolic content (TPC) in different oils increased during frying and strongly correlated with frying time. As frying progressed, it was observed that the rate of increase in TPC was relatively slower in PO than in the SO and CO. The shear stress versus shear rate results was fitted to Newtonian, Bingham and Herschel–Bulkley rheological models. The flow behaviour of fresh and fried SO, CO and PO was recorded at 25 °C. Fresh oils showed Newtonian behaviour with correlation coefficients greater than 0.99 at 25 °C and slight non-Newtonian behaviour after frying. Palm olein showed higher increase in viscosity in comparison to CO and SO. Rheological parameters of vegetables oils showed great changes, wherein the highest change in viscosity was recorded after 16 h of frying. Palm olein had higher flow behavior parameters than SO and CO. The increase in frying time caused an increase in K, η_B, τ_0HB, τ_0B, and η values, while the n values decreased with increasing the frying time. The viscosities of oils were plotted against the levels of C18:1 and C18:2 wherein highly positive correlations were found between them (R² = 0.99). The temperature dependence of viscosity was studied by using the Arrhenius relationship and the activation energy indicates the sensitivity of viscosity to changes in temperature. It could be concluded that the rheological parameters can provide an overall estimate of oil quality during frying.     

Pomelo Citrus grandis (L.) osbeck peel as an economical alternative substrate for fungal pectinase production

Polygalacturonase production by Aspergillus niger LFP-1 was studied in solid state fermentation (SSF) using pomelo (Citrus grandis) peel as a substrate. This local agricultural waste product is rich in lignocellulolytic material, including pectin, which can act as an inducer of pectinase production. Using the parameters of 5 g of 0.75 mm (particle size) pomelo peel as a substrate, moisture content ratio of 1:1 (w/v), inoculum size of 1×10⁷ spores/mL, cultivation temperature of 30°C, and no mixing, static fermentation conditions with addition of 1.2% ammonium nitrate produced the highest polygalacturonase production rate of 8.90 U/g of substrate and a fungal growth rate of 2.07mg of glucosamine/g of substrate on day 5 of cultivation. A large increase (1,434.5%) in enzyme production occurred after improvement of the growth parameters. Under optimum bioprocess conditions, pomelo peel can be used as solid substrate for production of pectinase.     

The Effect of Fermentation Temperature on the Microstructure,Physicochemical and Rheological Properties of Probiotic Buffalo Yoghurt

The properties of buffalo and bovine milk differ and the procedures developed to make bovine yoghurt may require optimisation for the production of buffalo yoghurt. This study aimed to apply cryo-scanning electron microscopy and confocal laser scanning microscopy to determine the optimal temperature for processing buffalo yoghurt. Milk was fermented at three different temperatures (37, 40 and 43 °C), stored for 28 days and the yoghurt microstructure, physicochemical and rheological properties assessed. Yoghurt fermented at 37 °C had a compact microstructure and the probiotic Lactobacillus acidophilus La-5 was more viable on storage. In contrast, yoghurt produced from a faster fermentation at 43 °C was firmer with a more porous microstructure that exhibited a higher degree of syneresis. The rheological properties during storage including the thixotropy, consistency coefficient and flow behaviour index were not significantly affected by temperature nor were the concentration of lactose, ionic calcium or titratable acidity. This study shows how changes to processing can be used to alter the microstructure of buffalo products and suggests that a decrease in fermentation temperature could be used to improve the quality of buffalo yoghurt.     

Effects of Anti-browning Combinations of Ascorbic Acid, Citric Acid, Nitrogen and Carbon Dioxide on the Quality of Banana Smoothies

The effects of 0.2 % ascorbic acid?+?0.2 % citric acid (AA?+?CA), 0.2 % ascorbic acid?+?0.2 % citric acid?+?N₂ (AA?+?CA?+?N₂) and 0.2 % ascorbic acid?+?0.2 % citric acid?+?CO₂ (AA?+?CA?+?CO₂) on the quality of banana smoothies were investigated. An obvious anti-browning effect was observed after each treatment, which resulted from a significant decrease in the polyphenol oxidase activity (p?<?0.05) and the exclusion of oxygen by infusion with inert N₂ or CO₂. The AA?+?CA?+?N₂ treatment exhibited the lowest change of browning index (ΔBI) indicating the best anti-browning effect on the banana smoothies. Compared with the Herschel–Bulkley model, the Power Law was less complex and more suitable for describing the rheological properties of the banana smoothies. AA?+?CA, AA?+?CA?+?N₂ and AA?+?CA?+?CO₂ treatments all significantly increased the pectin methylesterase activity of the banana smoothies (p?<?0.05). The AA?+?CA treatment increased the cumulative volume of the larger particles in the banana smoothies. The viscosity of the banana smoothies decreased after the three different treatments. In terms of the comprehensive results, the inclusion of AA?+?CA?+?N₂ in the production of banana smoothies was the best processing method applied.     

Efficient induction of inulin fructotransferase by inulin and by difructose anhydride III in Arthrobacter aurescens SK 8.001

Inulin fructotransferase (IFTase; EC 4.2.2.18) has received great attention mainly due to its application in producing difructose anhydride III (DFA III), which is a novel functional sweetener. The object of this study was to investigate the induction of IFTase in Arthrobacter aurescens SK 8.001 with various carbon sources, especially inulin and DFA III. IFTase production could be significantly promoted by the supplement of inulin (5–50 g/L) and DFA III (5–20 g/L). Inulin at high initial concentrations gave no indication of catabolite repression, whereas 30 and 40 g/L DFA III intensely inhibited cell growth and IFTase activity. No fructose was detected in broth throughout the cultivation with inulin, and inulin was converted into DFA III and minor fructooligosaccharides. And when DFA III was the carbon source, DFA III was the only sugar detected in the broth. In conclusion, both DFA III and inulin are effective for IFTase induction, and inulin with higher IFTase activity proved to be a more potent inducer.     

Establishment of a stable Amaranthus tricolor callus line for production of food colorant

This study aimed at demonstrating the effects of fermentation time (24, 48, 72, 96, and 120 h) and water activity (0.943, 0.970, and 0.985) on the production of cellulolytic enzymes by solid-state fermentation of purple mombin (Spondias purpurea L.) residue using Aspergillus niger. The fermentation was carried out at 35°C and the enzyme production was measured as endoglucanase and total cellulose activities. The optimum condition for endoglucanase was water activity 0.974 and 93.8 h of fermentation, reaching a production of 3.21 U/g of residue; whereas for total cellulase it was 0.958 and 79.4 h achieving 12.1 U/g of residue. Fermentation time had a greater effect on the endoglucanase activity, while water activity had a more significant influence on the total cellulase activity. Endoglucanase had optimum activity at temperature of 50°C and pH 5.0. Although cellulase total optimum activity was also at pH 5.0, the maximum activity was at 60°C.     

Artrocarpus heterophyllus—a potential substrate for citric acid biosynthesis using Aspergillus niger

The growing demand for citric acid and the need for alternative materials as substrates in the recent years has led to the choice of a novel and economically viable substrate namely, Artrocarpus heterophyllus for citric acid biosynthesis. A pilot scale study was done using this substrate and the conditions required for preparing a good substrate from jack fruit carpel fibre were optimized. Hydrolysis of jack fruit carpel fibre with 14.6 mol/l HCl, followed by fermentation with Aspergillus niger produced 73 g/l of citric acid in a period of 48 h. Enrichment of the medium was also tried by sugar supplementation and the efficiency of the fermentation medium thus prepared in producing citric acid was compared with the synthetic medium. The products of the microbial metabolism namely total titrable acidity, citric acid, intracellular proteins, extracellular proteins, amylase activity, lipid and biomass contents were determined periodically. Experimentally observed growth stages were used for mathematical modeling to estimate the kinetic parameters. The values calculated agree with the experimental ones.     

Application of plant essential oils in prevention of fungal growth on Para rubber wood

Antifungal activities of essential oils (cinnamon, clove, eucalyptus, peppermint and lemongrass oils) against moulds (Penicillium sp., Aspergillus niger and Aspergillus versicolor) isolated from rubber wood surfaces were examined. Clove oil possessed consistent antifungal activity with the minimal inhibitory concentration (MIC) of 5 μl ml^?1 against all these fungi, while cinnamon oil had MICs from 2.5 to 10 μl ml^?1. However, only dip treatment with cinnamon oil inhibited the growth of A. niger on rubber wood for at least 25 weeks.     

EFFECTS OF INTERMOLECULAR INTERACTIONS AND MOLECULAR ORIENTATION ON THE FLUX BEHAVIOR OF XANTHAN GUM SOLUTIONS DURING ULTRAFILTRATION

Conformational changes of xanthan gum as a function of concentration were investigated to elucidate its unusual flux behavior during ultrafiltration (UF). The contribution of hydrogen bonding on structure formation and the molecular orientation of xanthan gum on the flow characteristics were studied rheomechanically and rheo-optically. Known to affect xanthan structure at low concentrations, hydrogen bonding unexpectedly did not show significant influence on xanthan rheological properties up to 2 wt %. The ordered layers formed on the membrane surface proved responsible for the enhanced water removal during UF. This unique behavior could be attributed to the formation of aligned molecular orientation in addition to the viscosity increases during the biphasic region. Significant differences were observed between xanthan fermentation broth and solutions made of commercial xanthan, suggesting the need to control the salt concentration in fermentation broth in order to make UF an effective recovery process for xanthan gum after fermentation.

PRACTICAL APPLICATIONS

The knowledge gained from the present study strengthens fundamental understandings on the conformational changes of xanthan biopolymers during the recovery of xanthan gum from fermentation broth using ultrafiltration (UF). By taking advantage of the aligned molecular orientation, along with controlling the salt concentration in the fermentation broth, UF could be operated at elevated flux to speed up the removal of water from the viscous fermentation broth. The technology should find broad applications in the fermentation industry, especially where viscosity is of concern during the separation and purification of the product.     

A Viscoelastic Model for Honeys Using the Time–Temperature Superposition Principle (TTSP)

The viscoelastic parameters storage modulus (G′) and loss modulus (G″) were measured at different temperatures (5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, and 40 °C) using oscillatory thermal analysis in order to obtain a viscoelastic model for honey. The model (a 4th grade polynomial equation) ascertains the applicability of the time–temperature superposition principle (TTSP) to the dynamic viscoelastic properties. This model, with a regression coefficient higher than 0.99, is suitable for all honeys irrespective their botanical origin (monofloral, polyfloral, or honeydew). The activation energy (relaxation“ΔH _a” and retardation “ΔH _b”), and the relaxation modulus fit the model proposed. The relaxation modulus has a 4th grade polynomial equation evolution at all temperatures. The moisture content influences all the rheological parameters.     

Biological activities of lactobacilli relevant to cardiovascular health in skim milk

In this study, skim milk was fermented using 14 Lactobacillus strains for 16 h at 42 °C or for 48 h at 25 °C. On conclusion of fermentation, the proteolytic, angiotensin converting enzyme-inhibitory (ACE-I), and antioxidant activities as well as the inhibition of thrombin and cholesterol micellar solubility were determined. The results revealed that Lb. paracasei B-4564 exhibited the highest ACE-I activity (68.11%) under the 42 °C for 16 h condition, while Lb. rhamnosus B-1445 demonstrated the highest ACE-I activity (92.23%) under the 25 °C for 48 h condition. Lb. paracasei B-4564 exhibited the highest inhibition rate of thrombin (42.43 and 48.10%) and cholesterol (68.60 and 87.01%) under the 42 °C for 16 h and 25 °C for 48 h conditions, receptively. Lb. rhamnosus B-442 exhibited the highest DPPH radical scavenging activity of 95.63 and 62.89% under the 42 °C for 16 h and 25 °C for 48 h conditions, receptively. Lb. rhamnosus B-1445 demonstrated the highest Fe²⁺ chelating activity and reducing power under both the tested fermentation conditions.     

Comparison of physicochemical pretreatments of banana peels for bioethanol production

Pretreatments with different concentrations of sulfuric acid (0, 0.5, and 1% v/v) and temperatures (28 and 121 °C at 103 kPa in an autoclave) were performed on banana peels (BP) milled by mechanical grinding and grinding in a blender as well as without grinding. Cellulose, hemicellulose, lignin, ash, and total and reducing sugar contents were evaluated. The highest yields of cellulose enzymatic hydrolysis (99%) were achieved with liquefied autoclaved BP treated with 0.5 and 1% acid after 48 h of hydrolysis. Ethanol production by Kluyveromyces marxianus fermentation was assayed using hydrolyzed BP at 10, 15, and 20% (w/w). The highest ethanol level (21 g/L) was reached after 24 h of fermentation with 20% (w/w) BP. Kinetics of the consumption of reducing sugars under this fermentation condition demonstrates the presence of a lag period (about 8 h). Thus, BP are a good source for ethanol production.