Extracted substrate colour as an indicator of fungal growth in solid state fermentation

Aims: In solid state fermentation (SSF), estimation of biomass is difficult as fungal mycelium penetrates deep and remains attached to the solid substrate particles. This study examines and evaluates a new technique based on colour changes of fermented substrates during SSF as an indicator for fungal growth. Methodology and Results: SSF refers to microbial fermentation, which takes place in the absence or near absence of free water, thus being close to the natural environment in which the selected microorganisms, especially fungi, are naturally adapted. Although many promising methods are available, the evaluation of microbial growth in SSF may sometimes become difficult, impractical, and inaccurate. Essentially, this remains another critical issue for monitoring growth. In this study, measurements of colour changes of fermented substrates during SSF are used as indicators for growth and this technique has a potential to be used to quantify growth of microbes. For the growth of Aspergillus awamori and A. oryzae on wheat bran, soybean hulls, and rapeseed meal, it was confirmed that colour changes were directly proportional to the fungal growth. This new approach is an important complementation to the existing techniques, especially for basic studies. The advantages of this method are its ease of use, fast, non-destructive, cheap, and requires no special and expensive reagents. The key finding is that the colorimetric technique demonstrated in this study provides good means to estimate growth than that obtained by visual observation or spores counting.

Efficient production of lignocellulolytic enzymes xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by the mutant strain Aspergillus awamori 2B.361 U2/1

The production of xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by Aspergillus awamori 2B.361 U2/1, a hyper producer of glucoamylase and pectinase, was evaluated using selected conditions regarding nitrogen nutrition. Submerged cultivations were carried out at 30 ºC and 200 rpm in growth media containing 30 g wheat bran/L as main carbon source and either yeast extract, ammonium sulfate, sodium nitrate or urea, as nitrogen sources; in all cases it was used a fixed molar carbon to molar nitrogen concentration of 10.3. The use of poor nitrogen sources favored the accumulation of xylanase, β-xylosidase and ferulic acid esterase to a peak concentrations of 44,880; 640 and 118 U/L, respectively, for sodium nitrate and of 34,580, 685 and 170 U/L, respectively, for urea. However, the highest β-glucosidase accumulation of 10,470 U/L was observed when the rich organic nitrogen source yeast extract was used. The maxima accumulation of filter paper activity, xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by A. awamori 2B.361 U2/1 was compared to that produced by Trichoderma reesei Rut-C30. The level of β-glucosidase was over 17-fold higher for the Aspergillus strain, whereas the levels of xylanase and β-xylosidase were over 2-fold higher. This strain also produced ferulic acid esterase (170 U/L), which was not detected in the T. reesei culture.

Production and characterization of glucoamylase from fungus Aspergillus awamori expressed in yeast Saccharomyces cerevisiae using different carbon sources

Glucoamylase is widely used in the food industry to produce high glucose syrup, and also in fermentation processes for production beer and ethanol. In this work the productivity of the glucoamylase of Aspergillus awamori expressed by the yeast Saccharomyces cerevisiae, produced in submerged fermentation using different starches, was evaluated and characterized physico-chemically. The enzyme presented high specific activity, 13.8 U/mgprotein or 2.9 U/mgbiomass, after 48 h of fermentation using soluble starch as substrate. Glucoamylase presented optimum activity at temperature of 55ºC, and, in the substratum absence, the thermostability was for 1h at 50ºC. The optimum pH of activity was pH 3.5 - 4.0 and the pH stability between 5.0 and 7.0. The half life at 65ºC was at 30.2 min, and the thermal energy of denaturation was 234.3 KJ mol-1. The hydrolysis of different substrate showed the enzyme's preference for the substrate with a larger polymerization degree. The gelatinized corn starch was the substratum most susceptible to the enzymatic action.

A glucoamilase é amplamente utilizada na indústria de alimentos no processamento do amido para a produção de xarope com alto teor de glicose e também muito empregada nos processos de fermentação para produção de cerveja e etanol. Neste trabalho a glucoamilase de Aspergillus awamori expressa em Saccharomyces cerevisiae produzida sob fermentação líquida foi avaliada quanto à produtividade em diferentes amidos e caracterizada físico-quimicamente. A enzima apresentou alta atividade específica de 13,8 U/mg proteína e de 2,9 U/mg biomassa ao final de 48 h de fermentação em meio contendo amido solúvel. A glucoamilase apresentou temperatura ótima de atividade a 55ºC, e temperatura de desnaturação térmica na ausência de substrato por 1h a 50ºC. O pH ótimo de atividade foi na faixa de 3,5 - 4,0 e a estabilidade ao pH entre os valores 5,0 e 7,0. A meia vida a 65ºC foi 30,2 min., e a energia de desnaturação foi de 234.3 KJ mol-1. A hidrólise em diferentes substratos mostrou a preferência da enzima pelos substratos com maior grau de polimerização, sendo o amido de milho gelatinizado o substrato preferencial à ação enzimática.

Preliminary Discuss on Identification and Characterization of One Decolorizing Fungus / 微生物学通报

According to morphological and microscopic characteristics, a high-efficient decolorizing fungus, the strain Asaw117, was identified as Aspergillus awamori. Selecting eight different dyes from Azo dyes, anthraquinones dyes and oxygen Quinones dyes, the decolorizing assays of various dyes showed that the strain Asaw 117 was the highest decolorizing potential to 0.1 g/L Vat Blue RSN, the discoloration rate up to 100 percent. Comparing to different kinds of medium and several of carbon and nitrogen sources, the strain had the best decolorizing efficient although grew slower in the Czapek medium, otherwise, grew quicker and decolorizing efficient lower in the PDF medium. It could use Vat Blue RSN as a nitrogen source, but not as a carbon source. The medium composing of saccharose and ammonium nitrate as carbon and nitrogen sources was decolorizing potential markedly during different combinations of carbon and nitrogen sources. So the strain has good potential for the dyeing wastewater treatment