A high-throughput and reliable seedling bioassay to screen wheat germplasm for crown rot resistance was developed. Single wheat seedlings were grown in square seedling punnets in a glasshouse and inoculated with a monoconidial Fusarium pseudograminearum isolate 10 days after emergence. The punnets were laid horizontally on their side and a 10-µ L inoculum droplet placed on the stem base. Seedlings were incubated at near-saturated relative humidity, and crown rot severity was assessed 35 days after inoculation. Studies on the duration of incubation period, inoculum concentration and temperature were carried out to optimize these parameters. Seedling growth at 25/15( ± 5) ° C in a glasshouse and 48-h incubation at near-saturated RH in darkness gave the best results. When crown rot resistance rankings of 16 Australian cultivars from the bioassay were compared with their field performance, Spearman's rank correlation coefficient was highly significant. This indicated that the seedling bioassay mimicked field resistance to crown rot in adult plants. A bootstrap resampling analysis showed little or no improvement in the coefficient of variation with an increasing number of replications, indicating a high level of precision and reproducibility. By detecting small but consistent differences in crown rot severity, the bioassay proved effective in large-scale screening for partial resistance: already over 1400 wheat genotypes have been screened. The high degree of precision makes this an invaluable tool in the understanding of pathogen aggressiveness, host specialization and parasitic fitness.
Palm stearin fractionate (PSF), obtained from palm stearin by further fractionation with solvents and n-3 polyunsaturated fatty acids (n-3 PUFA) rich fish oil (FO) were subjected to interesterification at 1:1, 1:2, 1:3, 2:1 and 3:1 substrate molar ratio and catalyzed by lipase from Thermomyces lanuginosa for obtaining a product with triacylglycerol (TAG) structure similar to that of human milk fat (HMF). The parameters (molar ratio and time) of the interesterification reaction were standardized. The temperature of 60 °C and enzyme concentration of 10 % (w/w) were kept fixed as these parameters were previously optimized. The reactions were carried out in a stirred tank reactor equipped with a magnetic stirrer for 6, 12, 18 and 24 h. The blends were analyzed for fatty acid (FA) composition of both total FAs and those at the sn-2 position after pancreatic lipase hydrolysis. All the blended products were subjected to melting point determination and free fatty acid content. Finally, blend of PSF and FO at 2:1 molar ratio with 69.70 % palmitic acid (PA) content and 12 h of reaction produced the desired product with 75.98 % of PA at sn-2 position, 0.27 % arachidonic acid (AA), 3.43 % eicosapentaenoic acid (EPA) and 4.25 % docosahexaenoic acid (DHA) and with melting point of 42 °C. This study portrayed a successful preparation of TAG containing unique FA composition i.e. ≥ 70 % of the PA, by weight, were esterified at the sn-2 position which could be used in infant formulation with health benefits of n-3 PUFAs.
Lipase-catalyzed alcoholysis of soy phospholipids was investigated to simultaneously make lysophospholipids and fatty acid esters of individual alcohols. Alcoholysis was carried out by stirring a mixture of soy phospholipids and individual alcohols in equimolar proportions with 10% (by weight of reactants) Mucor miehei lipase at 55°C for 24 h. The products were isolated by column chromatography after removal of the lipase. Lysophospholipids (in 69-78% molar yield) were obtained from soy phospholipids, and the yield of esters of various alcohols also conformed nearly with theoretical yields. JAOCS 74, 597-599 (1997).KEY WORDS: Alcoholysis, column chromatography, longchain alcohol esters, lysophospholipid, Mucor miehei lipase, short-and long-chain alcohols, soy phospholipid.In recent years, lipase-catalyzed transformation reactions of lipids have become important for making ester derivatives from fats and oils for various specific applications (1,2). Phospholipids, which constitute a class of industrially important surfactants, are also receiving attention for various lipase-catalyzed transformations. The conversion of phospholipids to lysophospholipids and fatty acids is usually performed by the action of phospholipases A 1 and A 2 (3-5). There are also some triacylglycerol lipases that can cleave fatty acids from the sn-1 and/or sn-2 positions of diacylglycerophospholipids to yield lysophospholipids with useful functional properties (6-9).Conversion of phospholipid to lysophospholipid by reptilian phospholipases suffers from two distinct disadvantages. Considerable difficulties are faced in deactivation of the enzymes after completion of the reaction. Also, the phospholipases show poor activity in primary alcohols or in organic solvents (10,11). On the contrary, fungal lipases function perfectly well in nearly anhydrous alcohols, and some of them have been shown to accept phospholipid as substrate (12-15).We are aware of only two literature reports concerning synthesis of lysophospholipids from soy phospholipids by lipase-catalyzed alcoholysis. One communication, published by Samey et al. (16), shows the possibilities of modifying phospholipids by alcoholysis reaction with alcohols such as ethanol, isopropanol and n-butanol, catalyzed by lipase from Rhizomucor miehei, to produce lysophospholipids. In the other publication (17), lysophospholipids were produced by glycerolysis of soy phospholipids with an immobilized form of this same lipase as a catalyst.Production of long-chain alcohol esters of C 16 -C 18 fatty acids is industrially important because these quite hydrophobic compounds are widely used as lubricants, plasticizers, and in cosmetics. Depending on the chainlength of the fatty acids and alcohols, products vary in consistency from liquid to solid waxes (18). The production of long-chain alcohol esters of fatty acids by alcoholysis involving chemical catalysts is well established. However, there are certain disadvantages of the chemical catalyst route. It is nonspecific and leads to total conversion of f...
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