Daljit Singh Arora

Antimicrobial activity of spices

Spices have been shown to possess medicinal value, in particular, antimicrobial activity. This study compares the sensitivity of some human pathogenic bacteria and yeasts to various spice extracts and commonly employed chemotherapeutic substances. Of the different spices tested only garlic and clove were found to possess antimicrobial activity. The bactericidal effect of garlic extract was apparent within 1 h of incubation and 93% killing of Staphylococcus epidermidis and Salmonella typhi was achieved within 3 h. Yeasts were totally killed in 1 h by garlic extract but in 5 h with clove. Some bacteria showing resistance to certain antibiotics were sensitive to extracts of both garlic and clove. Greater anti-candidal activity was shown by garlic than by nystatin. Spices might have a great potential to be used as antimicrobial agents.

Antibacterial and phytochemical screening of Anethum graveolens, Foeniculum vulgare and Trachyspermum ammi.

BackgroundAnethum graveolens Linn., Foeniculum vulgare Mill. and Trachyspermum ammi L. are widely used traditional medicinal plants to treat various ailments. To provide a scientific basis to traditional uses of these plants, their aqueous and organic seed extracts, as well as isolated phytoconstituents were evaluated for their antibacterial potential.MethodsAntibacterial activity of aqueous and organic seed extracts was assessed using agar diffusion assay, minimum inhibitory concentration and viable cell count studies; and their antibacterial effect was compared with some standard antibiotics. The presence of major phytoconstituents was detected qualitatively and quantitatively. The isolated phytoconstituents were subjected to disc diffusion assay to ascertain their antibacterial effect.ResultsHot water and acetone seed extracts showed considerably good antibacterial activity against all the bacteria except Klebsiella pneumoniae and one strain of Pseudomonas aeruginosa. Minimum inhibitory concentration for aqueous and acetone seed extracts ranged from 20–80 mg/ml and 5–15 mg/ml respectively. Viable cell count studies revealed the bactericidal nature of the seed extracts. Statistical analysis proved the better/equal efficacy of some of these seed extracts as compared to standard antibiotics. Phytochemical analysis showed the presence of 2.80 – 4.23% alkaloids, 8.58 – 15.06% flavonoids, 19.71 – 27.77% tannins, 0.55–0.70% saponins and cardiac glycosides.ConclusionAntibacterial efficacy shown by these plants provides a scientific basis and thus, validates their traditional uses as homemade remedies. Isolation and purification of different phytochemicals may further yield significant antibacterial agents.

Ligninolytic Fungal Laccases and Their Biotechnological Applications

Lignin is amorphous in nature, lacks stereoregularity, and is not susceptible to hydrolytic attack. Despite its resistant nature, it is however degraded by various microorganisms, particularly, white-rot fungi. Such fungi are capable of extracellular production of lignin peroxidase, manganese peroxidase, and laccase, the three major enzymes associated with ligninolysis. Though all white-rot fungi do not produce all the three enzymes, laccase occupies an important place in ligninolysis. Laccase belongs to a diverse group of enzymes called oxidoreductases and is also known as benzenediol: oxygen oxidoreductase. They have low substrate specificity. The copper-containing enzyme laccase has been detected in a variety of organisms such as bacteria, fungi, plants, and insects. Mostly, these are extracellular proteins, although intracellular laccases have also been detected in some fungi and insects. Fungal laccases are believed to play a variety of roles, such as, morphogenesis, pathogenesis, and lignin degradation. As an oxidase, laccase is used in many agricultural, industrial, and medicinal applications. Current investigations are focused on laccase-based biooxidation, biotransformation, biosensor, and enzymatic synthesis of organic compounds. By enhancing laccase production using different physiochemical parameters, better understanding of the mechanism for the reactions of interest, and optimizing the catalytic activity of laccase, it can be used in a better way in diverse fields of biotechnology.

Involvement of lignin peroxidase, manganese peroxidase and laccase in degradation and selective ligninolysis of wheat straw

Some white-rot fungi have been studied to evaluate their potential to degrade wheat straw with specific reference to their ligninolytic ability and associated enzymes, viz. lignin peroxidase, manganese peroxidase, and laccase. The data have been compared with the much studied Phanerochaete chrysosporium. In the present study, Daedalea flavida and two of the Phlebia spp. were found to be capable of degrading lignin selectively and hence hold better prospects in various biotechnological applications than P. chrysosporium. Phlebia radiata and P. floridensis were the best producers of manganese peroxidase and laccase, respectively, whereas P. chrysosporium was best for lignin peroxidase.

Antibacterial activity of some Indian medicinal plants

Aqueous extracts of ten medicinal plants were examined for their antibacterial potential against some reference strains of human pathogenic bacteria. Anethum graveolens, Elettaria cardamomum, Foeniculum vulgare, Trachyspermum ammi and Viola odorata were found to be better/equally effective compared to standard antibiotics. V. odorata was the most effective antibacterial with minimum inhibitory concentration values ranging from 1 to 2%. The results provide a scientific basis for the centuries-old usage of aqueous extracts of these medicinal plants.

Effects of various media and supplements on laccase production by some white rot fungi.

White rot fungi produce three main extracellular enzymes involved in ligninolysis; laccase, lignin peroxidase and manganese peroxidase. Though all white rot fungi do not produce all three enzymes, laccase occupies an important place in ligninolysis. The present paper reports its production by some white rot fungi; Daedalea flavida, Phlebia brevispora, Phlebia radiata and Polyporus sanguineus under different nutritional conditions. Of the various basal media tested, mineral salts malt extract broth proved to be the best medium for laccase production. Sugarcane bagasse proved to be the best laccase inducer among the various supplements added to different media.

Comparison of two assay procedures for lignin peroxidase.

The most widely accepted assay for detecting lignin peroxidase, based on the oxidation of veratryl alcohol to veratraldehyde, suffers from some drawbacks. At 310 nm, the wavelength at which the assay is performed, some other materials like lignins, quinonic compounds and aromatics also exhibit strong absorbance thus interfering with the estimation when present in the media. The present study reports the lignin peroxidase production by some white rot fungi under different nutritional conditions. The veratryl alcohol oxidation assay procedure for lignin peroxidase has been compared with another method based on the oxidation of the dye azure B involving absorbance measurements in the visible range. The latter method proved to be much more advantageous over the veratryl alcohol oxidation method, in media supplemented with malt extract, lignin preparations and agricultural residues. The enzyme production by veratryl alcohol assay could be detected only in mineral salts broth. By the azure B assay the enzyme activity was detected in all the media tested. The supplements gave varied response in different media. Veratryl alcohol enhanced the enzyme production in malt extract broth and mineral salts malt extract broth. Among the lignin preparations Indulin AT increased the lignin peroxidase titres from 2 to 20 fold in different fungi. Similarly, wheat straw supplemented in mineral salts broth and malt extract broth, separately, strongly stimulated the lignin peroxidase production. The above studies revealed that azure B assay may act as a substitute or equivalent method.

Laccase production by some white rot fungi under different nutritional conditions

Abstract The role of laccase in ligninolysis has been disputed but it still seems to have an important place in the reactions. Trametes versicolor has been the organism of choice for laccase production. The present paper reports laccase production by Phlebia fascicularia , P. floridensis and Dichomitus squalens . Enzyme production in mineral salts broth, malt extract broth and in the presence of various supplements showed that P. floridensis and D. squalens were better laccase producers than T. versicolor . Different lignin preparations and natural agricultural residues gave the best enzyme production, except with T. versicolor . The studies underline the need to explore more organisms to fully exploit the potential of laccase-producing fungi.

Production of lignocellulolytic enzymes and enhancement of in vitro digestibility during solid state fermentation of wheat straw by Phlebia floridensis

Degradation by white rot fungi has the potential to increase digestibility of wheat straw and thus improve its value as animal feed. To optimize conditions for production of lignocellulolytic enzymes by Phlebia floridensis during solid state fermentation of wheat straw along with enhancement of in vitro digestibility, a response surface methodology (RSM) based experiment was designed. Effect of moisture content, inorganic nitrogen source (NH(4)Cl) and malt extract on lignocellulolytic enzymes, changes in chemical constituents and digestibility of wheat straw was evaluated. With increase in moisture content, laccase production increased up to 34-fold, while Manganese peroxidase was optimally produced in the presence of almost equal amount (50-55 mg/g of WS) of NH(4)Cl and malt extract. These supplements also significantly (p<0.05) enhanced the production of CMCase and xylanase. In vitro digestibility was increased by almost 50% with a loss of 27.6% and 14.6% in lignin and total organic matter, respectively. The present findings revealed P. floridensis to be an efficient organism for lignocellulolytic enzymes production and simultaneous enhancement in in vitro digestibility of wheat straw.

Biodecolourization of azo and triphenylmethane dyes by Dichomitus squalens and Phlebia spp.

Nine white-rot fungal strains were screened for biodecolourization of brilliant green, cresol red, crystal violet, congo red and orange II. Dichomitus squalens, Phlebia fascicularia and P. floridensis decolourized all of the dyes on solid agar medium and possessed better decolourization ability than Phanerochaete chrysosporium when tested in nitrogen-limited broth medium. Journal of Industrial Microbiology & Biotechnology (2002) 28, 201–203 DOI: 10.1038/sj/jim/7000222