Citric acid production by Aspergillus foetidus in batch and fed‐batch cultures

Abstract

Sucrose and ammonium nitrate, respectively, were the preferred carbon and nitrogen sources for citric acid production by Aspergillis foetidus CCRC 30206. For a 7‐day fermentation, the maximal citric acid production of 7.2 ～ 28.4 g/l appeared at an initial sucrose concentration of 12 % under various initial levels of nitrogen and phosphorous sources. Citric acid production commenced and ceased earlier in either the nitrogen‐limited (NH₄NO₃, 0.5g/l) or the phosphorous‐limited (KH₂PO₄, 0.2 g/1) medium. The richer media delayed the onset of citric acid production. Nonetheless, 48.3 g/1 of citric acid was produced in the medium rich in nitrogen (NH₄NO₃, 2.0 g/1) and phosphorous (KH₂PO₄, 1.4 g/1) when the batch culture was extended to 16 days. The cultivation time of this rich medium was reduced to 12 days in a fed‐batch culture under dual limitation of both nitrogen and phosphorous.     

Durability of particleboards made from wood particles chemically modified with propionic anhydride: results after six years in ground stake-test

Propionylated particleboard stakes with 12.2% propionyl content were tested in ground contact in Western Greece. The stakes showed severe attack after five years of testing and total decay after six years, whereas the unmodified boards showed total decay during the fourth year of testing.     

The development of wood technology and technology developments in the wood industries—from history to future

The term technology is frequently used in every-day communication and in the specific areas of producing goods and providing services. Technology comprises the science of knowledge and usage of tools and techniques or its systems, methods, organization and material products thereof. The meaning of the word technology itself as well as the specific meaning of the term wood technology has changed over the past centuries of industrialized production systems. The current paper analyses the development of wood technology over a period of about 300 years. Based on various COST Actions and the European Forest-sector Technology Platform current topics of wood technology are addressed and a future outlook is given.     

Estimating mechanical properties of clear wood from ten‐year‐old Melia azedarach trees using the stress wave method

The objective of this study was to examine the potential of stress wave velocity (SWV) as a rapid and non-destructive method to estimate the mechanical properties of Melia azedarach wood. The SWV, dynamic modulus of elasticity (MOE_d), modulus of elasticity (MOE), modulus of rupture (MOR, bending strength) and density were determined on ninety 20 ? 20 ? 320 mm clear wood specimens, obtained from stems of three ten-year-old M. azedarach trees, and tested at environmental equilibrium in 20°C, 60?% relative humidity (a moisture content of approximately 12?%). There was a statistically significant (0.1?% level) but weak correlation (R²?=?0.23) between the SWV and MOE, but no statistically significant correlation was found between the SWV and MOR. Much better results for prediction of static properties of M. azedarach wood were obtained when SWV and wood density (WD) were used together through calculation of MOE_d in the air-dry condition (MOE: R²?=?0.76, MOR: R²?=?0.47), although in the case of MOR a model based on WD alone is slightly better (R²?=?0.58), and WD is also almost as good as MOE_d for predicting MOE. It is concluded that SWV coupled with WD can be employed as a predicting parameter to evaluate the mechanical properties of M. azedarach wood during the manufacturing process, although WD alone is also effective. The SWV alone would not be useful due to MOE being almost directly proportional to WD at this moisture content.

     

Correlation between acoustic and physical–mechanical properties of insulating composite boards made from sunflower stalk and wood chips

Physical and mechanical properties of low-density insulating particleboards (0.45 g/cm³) made from wood chips and waste sunflower stalk (SFS) were studied, and correlations with the acoustic properties were determined. Two types of layered boards were manufactured, one with SFS in the central section, and the other with SFS on the surface layers; the layered boards were then compared with two kinds of homogeneous boards made from 100 % SFS and wood chips. Two types of resin were used, urea–formaldehyde (UF) and isocyanate; the press time was 5 and 7 min. Results showed that higher compression ratio in boards containing sunflower stalk resulted in significant improvement of physical–mechanical properties. Interaction between different layers of wood chips and sunflower stalk caused no clear trend in the acoustic properties of the layered boards with none of the resins; however, significant difference was found in the homogeneous boards produced with UF and isocyanate resins. High significant correlations were found between modulus of rupture and elasticity and thickness swelling (24 h) versus six acoustic properties. It can therefore be concluded that acoustic properties, as non-destructive tests, can be used to estimate some of the physical–mechanical properties of new insulating particleboards with different density and compositions.     

Dimensional stability of wood–plastic composites reinforced with potassium methyl siliconate modified fiber and sawdust made from beetle-killed trees

Wood from two varieties of beetle-killed trees was used to fabricate wood–plastic composites. Loblolly pine and lodgepole pine beetle-killed trees were defibrated mechanically and thermomechanically, respectively, into fiber. Fiber and sawdust produced from the trees were modified with potassium methyl siliconate (PMS) and injection-molded into fiber/sawdust reinforced plastic composites. Modification of fiber and sawdust with PMS improved the compatibility between lignocellulosic materials and ethylene plastic in the composites, resulting in decreased water sorption, increased dimensional stability, and increased tolerance to morphological variations in the fiber and sawdust. Fiber-to-sawdust ratio and size of sawdust particles affected the time required for saturation with water, as well as dimensional stability.     

Properties of oriented strandboard made of wood species from Brazilian planted forests: Part 1: 80 mm-long strands of Pinus taeda L.

This research is part of a general study on the properties of oriented strandboard (OSB) using wood strands of species from Brazilian planted forests. The OSB industry is the latest wood related activity established in Brazil. In this particular part of the study, 80 mm long strands of Pinus taeda L. were bonded using two resin types (urea-formaldehyde and phenol-formaldehyde) at two levels of resin content (5% and 8%) to produce three-layer cross-aligned OSB to a face to core layer ratio of 1:2 and target density of 0.75 g/cm³. Physical and mechanical properties of the boards were evaluated according to ASTM standard D 1037-96a (1997) and the results compared to standards available as requirements for commercial structural panels. The results indicate that all the mechanical properties evaluated were above the requirements set forth by the Canadian standard CSA O437.0 (1993) for structural panels. The results of Janka hardness were in average 4 folds higher than the minimal requirements for Grade R-1 waferboard. Screw withdrawal values were also above the minimum required by grade M-3 of ANSI A208.1 standard (1993). Nevertheless, values of thickness swelling and water absorption were very high. The low dimensional stability may be related to the high density of the boards (“springback” effect) and also to the fact that no wax was used.     

Odor compounds in cheese made from the milk of cows supplemented with extruded linseed and α-tocopherol

Three diets for cows were used to evaluate the effect of extruded linseed (EL) or extruded linseed plus α-tocopherol (ELVE) supplementation of a maize silage diet (CO) on the odor-active compounds of Saint-Nectaire cheese. Cheese odor and flavor profiles were studied by sensory analysis. The volatile compounds were extracted by purge and trap and separated by gas chromatography. The odor compounds were detected and identified using an 8-way olfactometric device and a mass spectrometer. Twenty-nine volatile compounds were considered as contributing to the odor of Saint-Nectaire cheese. Half the compounds identified were known to be lipid degradation products but not all of them were affected by the diet. Among the markers of unsaturated fatty acid degradation, hexanal was not affected, whereas heptanal was increased more by the ELVE diet (6 times) than by the EL (3 times) diet. The ELVE diet led to cheeses with butanoic acid and heptanal odor peaks that were, respectively, 2 and 6 times higher than with the CO diet, which explained the lower milk odor and flavor scores obtained by sensory analysis on ELVE cheese. Although the cheese-making date had a greater effect than the diet on the aromatic profiles of the cheese, principal component analysis showed that the differences between cheeses obtained on the 3 diets were repeatable. The EL diet successfully enhanced cheese nutritional value without noticeably changing its flavor. α-Tocopherol supplementation was found to be unnecessary, as no oxidized odor was found.     

Practical use of β-carotene-loaded nanoemulsion as a functional colorant in sausages made from goat meat surimi-like material

The potential applicability of β-carotene-loaded nanoemulsion (CNE) as a natural colorant in non-smoked sausage made from goat meat surimi-like material (GMS) was elucidated. The effect of CNE content (0–30 g 100 g⁻¹) on the physicochemical characteristic, oxidative stability and β-carotene remaining during cold storage (4 °C) was determined. The higher the CNE, the greater the a*, b* and redness index with the lower L*, and colour likeness score. CNE content had a little impact on the moisture content, a_w and pH of sausages over storage period. However, the expressible drip, breaking force and deformation were largely influenced by the CNE content. All CNE-containing sausages displayed a superior oxidative stability to control. Among CNE-incorporated samples, the lowest lipid oxidation and β-carotene degradation were noticeable in the sausage with 10 g 100 g⁻¹ CNE. Thus, the CNE at 10 g 100 g⁻¹ was a promising functional colorant for emulsion sausage made from GMS.     

Properties of phosphatase from six varieties of apricot relevant to potential use in apricot air‐drying

Abstract

Apricot phosphatase measured with p‐nitrophenol phosphate as substrate, was present as soluble and membrane‐bound isoforms at levels per gram of tissue generally lower than those found in other fruits, vegetables and cereals. Properties such as substrate affinity, stability at acid pH, heat stability at 50 to 60°C (normal apricot drying temperatures), optimal reaction temperature of 58°C, and reactivity with ascorbic acid polyphosphate favor the use of phosphatase to catalyze the slow release of ascorbic acid over the 36 to 40 h required for air drying. A feasibility trial demonstrated that low levels of ascorbic acid polyphosphate present in the infusion solution (0.5 to 2 g/L) were insufficient to prevent browning, but levels greater than 5 g/L resulted in commercially acceptable dried fruit.     

Influence of elicitors on alk(en)yl‐L‐cysteine sulfoxides and related amino acids in onion (Allium cepa) tissue cultures

Conditions were developed whereby onion tissue cultures could produce alk(en)yl‐L‐cysteine sulfoxides (ACSOs) at levels exceeding those in mature onion bulbs. Callus cultures grown in Gamborg's B5 basal medium with minimal organics supplemented with 2,4‐dichlorophenoxyacetic acid (at 2.5 μM) and 6‐benzyl‐aminopurine (at 1 μM) exhibited greening and partially differentiated roots within 6 months culture, and could be maintained for over 1 year. Within 10–12 months, callus cultures produced up to twice as much 1‐propenyl‐L‐cysteine sulfoxide (1‐PeCSO) and up to 6 times as much methyl‐L‐cysteine sulfoxide (MCSO) as found in mature onion bulbs. These callus cultures also had greater levels of glutamic acid, glycine and valine than mature onion bulbs. The supplementation of growth media with the elicitors, salicylic acid (SA), onion cell wall fragments (CWF) and acid‐cleaved chitosans (ACC) had differential effects of ACSO yields in 10–12 month old callus cultures. CWF suppressed tissue levels of both 1‐PeCSO and MCSO, SA suppressed tissue levels of MCSO more so than 1‐PeCSO, and ACC suppressed tissue levels of 1‐PeCSO with little effect on MCSO levels.     

Short communication: High frequency of β-lactam-resistant Staphylococcus aureus in artisanal coalho cheese made from goat milk produced in northeastern Brazil

Reports of β-lactam-resistant Staphylococcus aureus in artisanal goat cheese are increasing, and this phenomenon is relevant to public health. The objective of the present study was to determine the prevalence of S. aureus strains carrying the blaZ and mecA resistance genes, as well as the genes encoding the staphylococcal enterotoxins SEA, SEB, SEC, SED, SEE, and TSST-1 in artisanal coalho cheese made from goat milk produced in northeastern Brazil. We used biochemical and molecular tests to characterize 54 S. aureus isolates found in artisanal coalho cheese collected from commercial establishments producing animal products in 11 municipalities of Pernambuco State, Brazil. A PCR analysis revealed that 42.6% (23/54) of the isolates were positive for the blaZ gene, and 7.4% (4/54) were resistant to methicillin by phenotypic testing. We did not detect mecA or any genes encoding enterotoxins. The presence of S. aureus carriers of the blaZ gene and the identification of methicillin-resistant S. aureus strains are of concern for the health of consumers of this type of cheese.     

Effect of activated carbon on ochratoxin A reduction in “Pedro Ximenez” sweet wine made from off-vine dried grapes

The application effect of an activated carbon on Ochratoxin A (OTA) contents was studied in small-scale winemaking trials in musts from sun-dried grapes Pedro Ximenez variety. For this experiment a 2 × 3 × 4 factorial arrangement was used in the same batch, the factors being adsorbent (control and activated carbon), time (1, 2, and 3 h), and adsorbent dose (control, 0.12, 0.24, and 0.36 g/L). Immunoaffinity columns to sample clean-up and enzyme-linked immunosorbent technique were utilized for OTA determination. The two-parameter Freundlich equation was used to evaluate the adsorption data and the K _F values obtained ranging from 0.11 to 2.68. Activated carbon at 0.24 g/L dose was the most effective treatment to reduce OTA, up 70% in sweet wines. The mean percentages reduction of color parameters (intensity and tone) and total polyphenol index of the wines were 9.8, 3.5, and 4%, respectively. The study demonstrates that this treatment can be successfully applied as a suitable technique to reduce OTA contents of the musts and sweet wines during the early winemaking processes.