Current Biochemical Engineering (Discontinued) - Volume 3, Issue 2, 2016

The main goal of this study was the characterization of the extremophile xylanases produced by Anoxybacillus sp. strain 3M, a thermophilic bacterium isolated from terrestrial hot springs (temperature of 90°C) samples collected on S. Miguel, Azores, Portugal. In this context, several batch fermentations using different agroindustrial wastes as inducer substrates (BSG – Brewers’ spent grain, wheat straw, sugarcane bagasse, and corn cobs) were performed towards an optimal enzyme production. The results for xylanase production showed that the higher enzymatic levels were obtained in the growth medium containing 1% (w/v) BSG (1.34 U mL-1), indicating that the BSG was the best inducer substrate, but the xylanase activity was also observed when wheat straw (1.33 U mL-1), sugarcane bagasse (0.80 U mL-1), corn cobs (0.30 U mL-1) and commercial xylan (0.21 U mL-1) were used as inducers. The extracellular crude enzymatic extract produced by Anoxybacillus sp. 3M in optimized submerged fermentation with BSG, attaining a maximal xylanase activity of 1.41 U mL-1 (i.e. 5-fold higher than with xylan), was further characterized for its optimal temperature and pH and stability. The highest enzyme activity was observed at a temperature of 60ºC and pH 5.3, but the enzyme retained 100% of its original activity after 96 h at 60°C and pH 7.0 and it still maintained 46% activity after 28 days at the same conditions. At 60ºC, the enzyme also retained its activity for pH ranging from 7.0 to 10.5. In addition, a zymogram of native gel analysis of the different culture supernatants revealed the presence of an enzymatic complex with an apparent molecular weight ranging from 400-500 kDa. Further application of strain 3M enzymatic extract to commercial oat spelts xylan revealed the presence of xylose and xylooligosaccharides (XOS), mainly X2 and X3, in the hydrolyzates produced. So, the thermostable and alkalistable extracellular xylanases from Anoxybacillus sp. 3M are biocatalysts with high potential for the development of processes where lignocellulosics are converted to precursors for several biotechnological applications.

Tannin acyl hydrolase (E.C.3.1.1.20) is also known as tannase, which hydrolyses ester and depside bonds of tannins to produce gallic acid, glucose, and galloyl esters. It is an inducible enzyme which has wide applications in pharmaceuticals, food, beverage industries, and also potentially used in the treatment of tannery effluents. A lot of emphasis has been paid on the production aspects of tannase from different sources, the major sources for tannase are considered to be fungi and bacteria. Recently, much attention has been paid on the production of these enzymes from yeast sources by conventional and molecular biology approach, because of its shorter generation time and convenience towards molecular genetics. Yeast tannase also finds wide application, because of its similarity with that of tannase from mycelial fungi. This study reviews the yeast sources, modes of production, different molecular approaches used and possible applications of these yeast sources as a potential candidate for tannase production.

Retting may be defined as the separation of bast fibres from the core tissues of the stem. The methods of retting have witnessed technological advances based on intervention of microbial enzymes resulting in better quality of fibers. The traditional methods of retting namely water retting and dew retting suffered from several limitations like poor quality of fibers, comparatively large space and time requirement, dependence on weather conditions, huge manpower involvement, pollution and high cost of drying. The microbial enzymes predominately pectinases are becoming popular for retting of fibers owing to the fact that it results in high quality fiber, save time and is also ecofriendly. The enzymatic retting is now preferred over the traditional methods resulting in formulation of several commercial enzyme preparations like Flaxzyme and Viscozyme. The variability in types of natural fibers, different retting methods, intervention of microbial enzymes for retting of fibers, parameters for efficient retting aresome of the important highlights of this review.

Halophiles have distribution all over the world and are especially present in the saline conditions. They are commonly found in saline lakes, desert conditions, saline soils and sea water. Evolution has played a significant role in making them halotolerant. Extraordinary quality of halophiles does not limit to the resistance to the saline environment but they also have diverse contribution to the humans. They have been reported to produce biofuels, bioplastics and many industrial enzymes stable at extreme conditions. Researches on halophiles open a broad area of opportunities to the scientific community and to the industry.

A Bacillus subtilis strain previously isolated from treated tannery effluent was tolerant to a maximum of 1400 mg/L Cr(VI) and reduced 77% toxic Cr(VI) to less toxic Cr(III) within 24 hrs. at pH 8.5 and 35°C temperature under shaking condition (120 rpm). The chromate reductase enzyme was found to be membrane bound and it has been purified using ammonium sulphate fractionation, anionexchange chromatography and gel filtration chromatography on Sephadex G-75 by cell free extract of the bacterium. The enzyme was characterized based on optimal temperature, pH, metal ions and initial Cr(VI) concentration in the reaction mixture. Maximum chromate reductase activity was observed at pH 8.5 and 35ºC temperature. The enzyme was significantly active between pH 6.5-10.0 and was found to be stable between 30ºC-40ºC. The chromate reductase activity was slightly decreased with increasing “the concentration of Cr(VI). The enzymatic activity was completely inhibited by Hg(II) and As(III) while Ni(II), Cd(II), Mn(II), Zn(II), Pb (II) and Co (II) showed moderate effect on chromate reductase activity of Bacillus subtilis and the chromate reduction was enhanced by Cu(II) and Fe(III).

Our biosphere is under constant threat from continuing environmental pollution. Different approaches have been practiced to decipher anthropogenic environmental hazards. Green chemistry and use of enzymes like laccases are some of the most highlighted practices in reducing the adverse effects on our surroundings. Laccases are widespread enzymes belong to oxidase group present mainly in fungi, some higher plants and a few bacteria. These enzymes are studied well in detail in the last decades since they can catalyze the oxidation of variety of diamines, aromatic amines, phenolic compounds, lignin related compounds as well as environmental pollutants that are highly recalcitrant with simultaneous reduction of molecular oxygen to water. Laccases have great biotechnological and industrial potential because of their diverse functions: pigment formation, lignin degradation and detoxification of colored industrial effluents including xenobiotics mostly from the textile, petrochemical industries, paper and pulp. Laccases are multifunctional enzymes which can be used for the manufacture of anti-cancer drugs, in certain water purification systems as cleaning agents, as bioremediation agent and even as ingredient of several cosmetics. Laccases can be further used in beverage processing, as biosensor to improve food sensory parameter, for ascorbic acid determination and for sugar gelation of beet pectin. This review focuses on the structure, properties and scope of laccases mainly in bioremediation and also in other industrial fields.

Pseudozyma sp. SPJ and its extracellular pectinase were used for animal feed pretreatment process. The four commonly used animal feed substrates viz. wheat straw, rice straw, corn seeds and green stem of sorghum were treated with pectinase (alone) and in combination with cellulase produced by Flavobacterium bolustinum. Significant results were obtained at 50°C of incubation temperature for 6-8 h. Wheat straw was found to be the best treated feed substrate. Pectinase and cellulase treatments resulted in appreciable release of reducing sugars and soluble protein with significant weight loss. Pseudozyma sp. SPJ also grew effectively on all the feed substrates without using any media supplement. The pectinase activity of 82.20 to 90.65 IU g-1 (dry substrate) was found in the culture filtrates. Wheat straw, rice straw, corn seeds and sorghum stem loosed 39.2%, 19.5%, 77.4% and 34.6% of their dry weight, respectively after 72 h of incubation. This pretreatment process liquefies the animal feed with increase in the available protein and energy content. It may reduce the feed cost and also the environmental pollution.

Nutritional attributes of cooked and solid-substrate fermented cooked kernels of Canavalia cathartica of the coastal sand dunes of southwest India by Rhizopus oligosporus were compared. Fermentation resulted in significant increase of crude protein, total lipids and six minerals (Na, K, Ca, Cu, Zn and Se). Fermented kernels meet NRC-NAS standard of four minerals for infants (K, Fe, Cu and Zn). The Na/K ratio of fermented kernels attained desired level (<1) to control the blood pressure. Fermentation significantly enhanced the true protein, albumin, globulin, glutelin and non-protein nitrogen. Among the essential amino acids, lysine was significantly increased, while histidine and tryptophan were confined only to fermented kernels. Except for histidine and tryptophan, rest of the essential amino acids showed high score in cooked as well as fermented kernels fulfilling FAO-WHO-UNU standard for adults. The in vitro protein digestibility was also significantly increased in fermented kernels. In cooked and fermented kernels, the mean protein efficiency ratio ranged between 0.77 and 1.14. The oleic acid was highest followed by plamitoleic acid in cooked as well as fermented kernels. The latter has attained significantly high quantity as a result of fermentation. Overall, fermentation of cooked kernels selectively improved the nutritional attributes favoring desired quantities of bioactive principles.

This study is aimed to determine the properties of Nantes carrots while drying by hot air at three different temperatures (50, 60 and 70 ºC). The chemical properties evaluated were: moisture, protein, fibre, ash, sugars and water activity, and the physical properties were: texture, color, density and porosity. The results showed that the drying at 70 ºC affected mostly the chemical properties analyzed. Regarding the texture, similar changes were recorded in terms of hardness, gumminess and chewiness at the temperature of 70 ºC that affected these properties the most. Regarding color, in general the variations in a* and b* along drying were not meaningful, although some discoloration was observed (increase in L*). The porosity increased due to the decrease in humidity. The final porosity measured for the carrots dried at 70 ºC was; however, lower than those for 50 and 60 ºC.

Serogroup C polysaccharide from Neisseria meningitidis (PS) constitutes the antigen for the respective vaccine production. In order to investigate the enhancement of the final PS concentration (Pf), as well as the overall yield factor (PS/biomass) (YP/X), 13 total cultivations distributed in 6 series (from A to F) were carried out in Frantz medium (40 L plus inoculum) in a 80L bioreactor at 35oC, 0.4 atm, 120 rpm, airflow rate of 5 L/min and KLa = 4.2 h-1. The series (A-F) correspond to different experimental conditions as follows: A) without pH and dissolved O2 controls; B) pH control at 6.5; C) pH control at 6.5 and glucose pulse at the 10th hour; D) dissolved O2 control at 10% saturation value; E) pH control at 7.4; F) dissolved O2 limitation (set rotation at 55 rpm). Concentrations of dry biomass, PS, cellular nitrogen, residual glucose, organic and inorganic nitrogen in the medium were measured. The best results were represented by series A (averages of Pf = 0.15 g/L and YP/X = 107 mg/g). The presented findings could be useful for a proper Frantz medium reformulation in order to obtain a greater amount of PS and improve the vaccine development in industrial scale-up production.