Collagenolytic Activity of Cured Hide Bacteria

S ummary : The aerobic and anaerobic collagenolytic activities of bacterial populations from 1 Australian and 2 South African cured hide samples at 0·85, 2·34, 7·0 and 10·0% of NaCl are described. The rate of denaturation of pure, undegraded collagen was determined by the release of amino acids and considerable collagenolysis was demonstrated. Collagenolytic activity was highest under aerobic conditions. Australian hides which produce uniformly good leather with little or no decay lacked collagenolytic bacteria.     

Chitosan/Collagen Hydrolysate Based Films Obtained from Hide Trimming Wastes Reinforced with Chitosan Nanoparticles

One of the long-standing problems of the leather manufacturing industry is that tons of solid leather waste generated during production meet environmental standards. Among all these solid wastes, untanned trimming wastes are of primary interest because of their relative collagen content, and therefore, in this research, hide trimming wastes from tanneries were used to prepare biodegradable films. The SDS-PAGE results suggested that obtained collagen hydrolysate (CH) was in its natural molecular form. Chitosan nanoparticles (CSNPs) were synthesized by ionotropic gelation technique with chitosan (CS) and tripolyphosphate anions and used in the preparation of CS/CH/CSNPs films containing different concentrations of CSNPs. The incorporation of CSNPs in CS/CH films has positively improved the films' remarkable physical properties. The DSC result showed that CS/CH films incorporated with CSNPs had higher glass transition and melting temperature. As a result, it was determined that CS/CH/CSNPs nanocomposite films have a high potential in biodegradable film systems.

     

Short-term batch studies on biological removal of chromium from synthetic wastewater using activated sludge biomass

Biological treatment of Cr(VI)-containing wastewater has drawn much attention recently as a method to treat environmental Cr(VI) contamination. The activated sludge method, due to its convenient operation and easy-to-scale-up, has been widely applied to treat municipal wastewater and some industrial wastewaters. In order to develop a suitable technique using activated sludge as the biomass to continuously remove Cr(VI) from wastewater, this paper investigated in short-term batch experiments the environmental elements affecting chromium biological removal from synthetic wastewater. The dissolved oxygen (DO), Cr(VI) initial concentration, biomass density, temperature, glucose content in the influent and contact time were observed to strongly influence chromium removal. It was found that the chromium removal efficiency decreased with the increase of DO and Cr(VI) initial concentration as well as glucose content in the feed, but increases in temperature and contact time improved the chromium removal efficiency. Although raising biomass concentration resulted in an increased chromium removal efficiency under both anaerobic and aerobic conditions, its influence on specific chromium removal was not significant.     

乳酸菌的抗冷冻性及耐受机理

乳酸菌发酵剂在工业生产过程中,会受到冷冻的刺激,如真空冷冻干燥及后期的低温保藏,此外,发酵乳制品的保藏和干酪的成熟过程也都在低温中进行。这些均会对乳酸菌发酵剂及发酵乳制品质量产生一定的影响。因此,掌握乳酸菌在冷冻条件下的反应机理有助于优化发酵剂和发酵乳制品在工业生产中的冷冻、发酵和贮藏条件,从而提高产品质量和生产效益。本文对乳酸菌的抗冷冻性及机理进行了分析,并对发酵剂的保护提出具体措施。     

Optimization of the unhairing leather processing with enzymes and the evaluation of inter-fibrillary proteins removal: an environment-friendly alternative

In this work is described the isolation of a new proteases-producing strain of Bacillus subtilis, screened from aerobic tannery sludge, to be applied in leather production. The optimization of culture conditions to enhance the proteolytic activity was carried out using central composite design. The enzymatic extract was characterized and the hide unhairing and the inter-fibrillary removal capabilities of the enzymatic extract were evaluated by scanning electron microscopy and by the determination of proteoglycans and glycosaminoglycans. The leather quality obtained with this enzymatic preparation was assessed for possible damages to hide collagen by measuring the amount of hydroxyproline released into the reaction medium. Temperature was the most significant factor for culture conditions optimization. The crude enzymatic extract showed the best values for proteolytic activities at pH 9 and 10, temperature between 37 and 55?°C, and showed good thermal stability up to 45?°C. The treated hides presented few remaining hairs; for the enzymatic process, the removal of inter-fibrillary proteins was approximately fourfold for glycosaminoglycans and sixfold for proteoglycans, when compared with the conventional unhairing process. The enzyme application was successful for hide treatment, suggesting that this enzymatic preparation can be used in an environment-friendly leather production to replace the conventional chemical process.     

Determination of total chromium in tanned leather samples used in car industry

Despite the high competition of synthetic fibers leather is nowadays still widely used for many applications. In order to ensure a sufficient stability of the skin matrix against many factors, such as microbial degradation, heat and sweat, a tanning process is indispensable. Using chromium (III) for this purpose offers a multitude of advantages, thus this way of tanning is widely applied. During the use of chromium tanned leather as clothing material as well as for decoration/covering purposes, chromium is extracted from the leather and may then cause nocuous effects to human skin, e.g. allergic reactions. Thus the knowledge of the total chromium content of leather samples expected to come into prolonged touch with human skin is very important. In car industry leather is used as cover for seats, steering wheel and gearshift lever The chromium contents often chromium tanned leather samples used in car industry were determined. First all samples were dried at 65 degrees C overnight and then cut in small pieces using a ceramic knife, weighed and analyzed by inductively coupled plasma--optical emission spectrometry (ICP-OES) after acidic microwave assisted digestion. The total chromium amounts found were in the range from 19 mg/g up to 32 mg/g. The extraction yield of chromium from leather samples in sweat is approximately 2-7%. Thus especially during long journeys in summer chromium can be extracted in amounts which may cause nocuous effects for example on the palm of the hands or on the back.     

The effect of various pre‐treatment methods of chromium leather shavings in continuous biogas production

During leather manufacture, high amounts of chromium shavings, wet by‐products of the leather industry, are produced worldwide. They are stable towards temperatures of up to 110°C and enzymatic degradation, preventing anaerobic digestion in a biogas plant. Hitherto, chromium shavings are not utilized industrially to produce biogas. In order to ease enzymatic degradation, necessary to produce biogas, a previous denaturation of the native structure has to be carried out. In our projects, chromium shavings were pre‐treated thermally and mechanically by extrusion and hydrothermal methods. In previous works, we intensively studied the use of these shavings to produce biogas in batch scale and significant improvement was reached when using pre‐treated shavings. In this work, a scale‐up of the process was performed in a continuous reactor using pre‐treated and untreated chromium shavings to examine the feasibility of the considered method. Measuring different parameters along the anaerobic digestion, namely organic matter, collagen content, and volatile fatty acids content, it was possible to show that a higher methane production can be reached and a higher loading rate can be used when feeding the reactor with pre‐treated shavings instead of untreated chromium shavings, which means a more economical and efficient process in an industrial scenario.     

The effects of treating bovine hide with steam at subatmospheric pressure on bacterial numbers and leather quality

AIMS: To examine the effect of subatmospheric steam treatment on total viable counts (TVCs) on bovine hide and on the quality of derived leather. METHODS AND RESULTS: Pieces of bovine hide were heated to 75 degrees C (+/-2 degrees C) (n = 3) or 80 degrees C (+/-2 degrees C) (n = 3) for periods of 1, 10 or 20 s by the application of steam at subatmospheric pressure in a laboratory scale apparatus. Treated hide pieces and untreated controls were tanned and the quality of leather was assessed. Treatment at 80 degrees C (T80) reduced the TVC on hide pieces by 2.95 (1 s), 3.33 (10 s) and 3.99 (20 s) log10 CFU cm-2 (P > 0.05). Treatment at 75 degrees C (T75) reduced the TVC on hide pieces by 1.87 (1 s), 2.51 (10 s) and 2.56 (20 s) log10 CFU cm-2 (P > 0.05). The grain on all treated hides was damaged resulting in sueding on derived leather. Sueding was observed on 100% of surfaces from T80-treated samples and on 18 (1 s) to 84% (20 s) of the surfaces of T75 samples. CONCLUSIONS: The magnitude of TVC reductions achieved using T75 and T80 could limit the impact and scale of contamination transfer to the carcass during dehiding. However, because of the sueding observed on derived leather, it is unlikely that either T75 or T80 would be a commercially valid operation during routine slaughter operations. SIGNIFICANCE AND IMPACT OF THE STUDY: Hide decontamination would provide an important critical control point for beef processing, however there are currently no commercially available treatments.     

Production and partial characterization of dehairing protease from Bacillus cereus MCM B-326

Bacillus cereus MCM B-326, isolated from buffalo hide, produced an extracellular protease. Maximum protease production occurred (126.87+/-1.32 U ml(-1)) in starch soybean meal medium of pH 9.0, at 30 degrees C, under shake culture condition, with 2.8 x 10(8) cells ml(-1) as initial inoculum density, at 36 h. Ammonium sulphate precipitate of the enzyme was stable over a temperature range of 25-65 degrees C and pH 6-12, with maximum activity at 55 degrees C and pH 9.0. The enzyme required Ca(2+) ions for its production but not for activity and/or stability. The partially purified enzyme exhibited multiple proteases of molecular weight 45 kDa and 36 kDa. The enzyme could be effectively used to remove hair from buffalo hide indicating its potential in leather processing industry.     

Hide depilation and feather disintegration studies with keratinolytic serine protease from a novel Bacillus subtilis isolate

Keratinases play an important role in biotechnological applications such as improvement of feather meal, enzymatic dehairing and production of amino acids or peptides from high molecular weight substrates. Bacillus subtilis P13, isolated from Vajreshwari hot spring (45–50°C) near Mumbai, India, produces a neutral serine protease and has an optimum temperature of 65°C. This enzyme preparation was keratinolytic in nature and could disintegrate whole chicken feathers, except for the remnants of shafts. The enzyme preparation also exhibited depilation of goat hides with the recovery of intact animal hair. The enzyme preparation could release peptides from ground feathers and bring about their weight reduction; however, similar action on hair was relatively weak. A single major PMSF-sensitive protease band could be detected upon zymogram analysis, indicating that a single enzyme may be responsible for feather degradation and hide depilation. The importance of these findings in the biotechnological application for feather and leather industries is discussed.     

Production of an alkaline protease by Bacillus cereus MCM B-326 and its application as a dehairing agent

The present investigation describes microbial production of an alkaline protease and its use in dehairing of buffalo hide. Bacillus cereus produced extracellular protease when grown on a medium containing starch, wheat bran and soya flour (SWS). The ammonium sulphate precipitated (ASP) enzyme was applied for dehairing of buffalo hide. Microscopic observation of longitudinal section of buffalo hide revealed that the epidermis was completely removed and hair was uprooted leaving empty follicles in the hide. The ASP enzyme was stable for one month at ambient temperature between 25–35 °C. Enzymatic dehairing may be a promising shift towards an environment-friendly leather processing method.     

Influence of Dietary Protein Level and the Amino Acids Methionine and Lysine on Leather Properties of Blue Fox (Alopex Lagopus) Pelts

The influence of dietary protein, methionine, and lysine on leather quality in blue fox pelts was studied. The pelt material originated from animals in two consecutive feeding trials (Exp. 1 and Exp. 2) with three protein levels: conventional, slightly lowered, and very low. The two lowest protein diets were fed as such or as supplemented with methionine or with lysine (lysine only in Exp. 2). The following physical leather properties were measured: breaking load (BRL), tensile strength (TEN), relative elongation at break (PEB), straining of skins at pelting, and shrinkage at dressing. A decline in the dietary protein content reduced BRL and, hence, leather firmness, and increased straining and the corresponding shrinking in Exp. 1. The supplemented methionine tended to improve leather strength and elasticity by increasing TEN and PEB in Exp. 1, whereas lysine elicited no response. Methionine supplementation at the slightly lowered protein level increased BRL in both experiments by almost 10% as compared with the respective non-supplemented diet. We conclude that with high protein quality diets, a level of 200g/kg DM (as digestible protein) appears to be adequate for producing pelts with firm, elastic leather, provided that an adequate amount of methionine is included in the diet.     

采后光照条件对白凤桃果实品质和挥发性香气物质形成的影响

研究了白凤桃果实贮藏过程中光照条件对果实成熟的影响。在7月12日(未熟期)和7月16日(硬熟期)采收果实,分别贮藏在光条件(白色荧光灯照明,果顶部光强为80μmol m~(-2)s~(-1))和暗条件中,室温均为25℃。硬熟期采收果实贮藏在光条件下,达到完熟期时,乙烯生成量较低。果肉的硬度在各个采收期,各种贮藏条件下均没有差别。光条件贮藏果实中花青苷含量较高。未熟期采收果实贮藏在光条件下时,可溶性固形物含量增加较多。光条件贮藏果实中天冬酰胺的下降比暗贮藏果实中更多。各时期采收的果实中,在光下贮藏时,果肉和果皮γ-癸内酯和γ-十二内酯的含量都明显增加。以上结果表明,白凤桃果实采收后在光下贮藏,可以明显改善果实的品质。     

Characterization of thermo- and detergent stable serine protease from isolated Bacillus circulans and evaluation of eco-friendly applications

Alkaline protease from Bacillus circulans has been purified and characterized in detail for its robustness and its eco-friendly application potential at leather processing and detergent industries. The molecular weight of the purified enzyme was estimated to be 39.5 kDa on SDS-PAGE. It exhibited optimum activity at broad temperature range and maximum at 70 °C under alkaline pH environment, in the presence of surfactants and oxidizing agents. It has revealed stain removal property and dehairing activity for animal hide without chemical assistance and without hydrolyzing fibrous proteins. This enzyme showed application potential in leather processing industry for production of better quality product in eco-friendly process. In addition, the stability (pH, temperature and surfactants) and hydrolysis of blood stain data also revealed its application in detergent industries.     

Isolation and characterization of a freeze-tolerant diploid derivative of an industrial baker's yeast strain and its use in frozen doughs

The routine production and storage of frozen doughs are still problematic. Although commercial baker's yeast is highly resistant to environmental stress conditions, it rapidly loses stress resistance during dough preparation due to the initiation of fermentation. As a result, the yeast loses gassing power significantly during storage of frozen doughs. We obtained freeze-tolerant mutants of polyploid industrial strains following screening for survival in doughs prepared with UV-mutagenized yeast and subjected to 200 freeze-thaw cycles. Two strains in the S47 background with a normal growth rate and the best freeze tolerance under laboratory conditions were selected for production in a 20-liter pilot fermentor. Before frozen storage, the AT25 mutant produced on the 20-liter pilot scale had a 10% higher gassing power capacity than the S47 strain, while the opposite was observed for cells produced under laboratory conditions. AT25 also retained more freeze tolerance during the initiation of fermentation in liquid cultures and more gassing power during storage of frozen doughs. Other industrially important properties (yield, growth rate, nitrogen assimilation, and phosphorus content) were very similar. AT25 had only half of the DNA content of S47, and its cell size was much smaller. Several diploid segregants of S47 had freeze tolerances similar to that of AT25 but inferior performance for other properties, while an AT25-derived tetraploid, TAT25, showed only slightly improved freeze tolerance compared to S47. When AT25 was cultured in a 20,000-liter fermentor under industrial conditions, it retained its superior performance and thus appears to be promising for use in frozen dough production. Our results also show that a diploid strain can perform at least as well as a tetraploid strain for commercial baker's yeast production and usage.     

Isolation and Characterization of a Freeze-Tolerant Diploid Derivative of an Industrial Baker's Yeast Strain and Its Use in Frozen Doughs

The routine production and storage of frozen doughs are still problematic. Although commercial baker's yeast is highly resistant to environmental stress conditions, it rapidly loses stress resistance during dough preparation due to the initiation of fermentation. As a result, the yeast loses gassing power significantly during storage of frozen doughs. We obtained freeze-tolerant mutants of polyploid industrial strains following screening for survival in doughs prepared with UV-mutagenized yeast and subjected to 200 freeze-thaw cycles. Two strains in the S47 background with a normal growth rate and the best freeze tolerance under laboratory conditions were selected for production in a 20-liter pilot fermentor. Before frozen storage, the AT25 mutant produced on the 20-liter pilot scale had a 10% higher gassing power capacity than the S47 strain, while the opposite was observed for cells produced under laboratory conditions. AT25 also retained more freeze tolerance during the initiation of fermentation in liquid cultures and more gassing power during storage of frozen doughs. Other industrially important properties (yield, growth rate, nitrogen assimilation, and phosphorus content) were very similar. AT25 had only half of the DNA content of S47, and its cell size was much smaller. Several diploid segregants of S47 had freeze tolerances similar to that of AT25 but inferior performance for other properties, while an AT25-derived tetraploid, TAT25, showed only slightly improved freeze tolerance compared to S47. When AT25 was cultured in a 20,000-liter fermentor under industrial conditions, it retained its superior performance and thus appears to be promising for use in frozen dough production. Our results also show that a diploid strain can perform at least as well as a tetraploid strain for commercial baker's yeast production and usage.     

Optimising the viability during storage of freeze-dried cell preparations of Campylobacter jejuni

Freeze-dried cultures of Campylobacter jejuni are used in the food and microbiological industry for reference materials and culture collections. However, C. jejuni is very susceptible to damage during freeze-drying and subsequent storage and it would be useful to have longer-lasting cultures. The survival of C. jejuni during freeze-drying and subsequent storage was investigated with the aim of optimising survival. C. jejuni was freeze-dried using cultures of different age (24-120 h), various lyoprotectants (10% phytone peptone, proteose peptone, peptonized milk, trehalose, soytone and sorbitol), various storage (air, nitrogen and vacuum) and re-hydration (media, temperature and time) conditions. One-day-old cultures had significantly greater survival after freeze-drying than older cultures. The addition of trehalose to inositol broth as a lyoprotectant resulted in almost 2 log(10) increase in survival after 2 months storage at 4 degrees C. Storage in a vacuum atmosphere and re-hydration in inositol broth at 37 degrees C increased recovery by 1-2 log(10) survival compared to re-hydration in maximal recovery diluent (MRD) after storage at 4 degrees C. Survival during storage was optimal when a one-day-old culture was freeze-dried in inositol broth plus 10% (w/v) trehalose, stored under vacuum at 4 degrees C and re-hydrated at the same incubation temperature (37 degrees C) in inositol broth for 30 min. The results demonstrate that the survival of freeze-dried cells of C. jejuni during storage can be significantly increased by optimising the culture age, the lyoprotectant, and the storage and re-hydration conditions. The logarithmic rate of loss of viability (K) followed very well an inverse dependence on the absolute temperature, i.e., the Arrhenius rate law. Extrapolation of the results to a more typical storage temperature (4 degrees C) predicted a very low K value of 1.5 x 10(-3). These results will be useful to the development of improved reference materials and samples held in culture collections.     

Collection of chromium (III) by sulfite and sisulfite chitosans

Abstract

Chromium (III) collection on sulfite (CS) and bisulfite (CBS) chitosans was investigated in order to obtain information about chromium recovery from tannery wastes from the chromium leather process. Collection of Cr(III) by sulfite and bisulfite chitosans was fast during the first 60 minutes and was affected by the pH of the solution, contact time and temperature. Chromium collected on bisulfite was easily eluted with dilute sulfuric acid solution.     

Optimization of native agar extraction from Hydropuntia cornea from Yucatán, México

Response surface methodology (RSM) was used to determine optimum extraction conditions for yield, gelling temperature, melting temperature and apparent viscosity of native agar from the red alga Hydropuntia cornea. Two independent variables were selected during extraction, temperature (80, 90 and 100 degrees C) and time (2, 3 and 4 h). The extraction procedure using 100 degrees C and 3 h produced the greatest yield (43.3%), the greatest gelling temperature (32 degrees C) and the greatest melting temperature (78 degrees C). The extraction using 65 degrees C and 4 h produced the optimum statistical apparent viscosity (80.73 cPs), though agar yield under these conditions had low quality for industrial purposes. Temperature and time do not affect melting temperature, but do play an important role in gelling temperature. From the independent variables studied, extraction temperature is most important in producing an increase in yield, and time is the only variable that contributes significantly to increasing viscosity. Most of the physicochemical properties found in the native agar from H. cornea extracted at 100 degrees C/3 h were similar to commercial samples. These findings suggest the feasibility of using this colloid in spreads and soft-texture food products.