Interspecific evolutionary relationships of alpha-glucuronidase in the genus Aspergillus.

The increased availability and production of lignocellulosic agroindustrial wastes has originated proposals for their use as raw material to obtain biofuels (ethanol and biodiesel) or derived products. However, for biomass generated from lignocellulosic residues to be successfully degraded, in most cases it requires a physical (thermal), chemical, or enzymatic pretreatment before the application of microbial or enzymatic fermentation technologies (biocatalysis). In the context of enzymatic technologies, fungi have demonstrated to produce enzymes capable of degrading polysaccharides like cellulose, hemicelluloses and pectin. Because of this ability for degrading lignocellulosic material, researchers are making efforts to isolate and identify fungal enzymes that could have a better activity for the degradation of plant cell walls and agroindustrial biomass. We performed an in silico analysis of alpha-glucoronidase in 82 accessions of the genus Aspergillus. The constructed dendrograms of amino acid sequences defined the formation of 6 groups (I, II, III, IV, V, and VI), which demonstrates the high diversity of the enzyme. Despite this ample divergence between enzyme groups, our 3D structure modeling showed both conservation and differences in amino acid residues participating in enzyme-substrate binding, which indicates the possibility that some enzymes are functionally specialized for the specific degradation of a substrate depending on the genetics of each species in the genus and the condition of the habitat where they evolved. The identification of alpha-glucuronidase isoenzymes would allow future use of genetic engineering and biocatalysis technologies aimed at specific production of the enzyme for its use in biotransformation.

Potential functional bakery products as delivery systems for prebiotics and probiotics health enhancers.

Several health benefits have been associated to probiotics and prebiotics, most of these are involved in the regulation of the host's gut microbiome. Their incorporation to diverse food products has been done to develop potential functional foods. In the case of bakery products, their incorporation has been seen to improve several technological parameters such as volume, specific volume, texture along with sensorial parameters such as flavor and aroma. Scientific literature in this topic has been divided in three main research branches: nutrition, physical quality and sensory analyzes, however, studies rarely cover all of them. Due to the harsh thermal stress during baking, sourdough technology along with microencapsulation of probiotics, has been studied as an alternative to enhance its nutritional values and increase cell viability, though in few occasions. The potential functional baked goods have maintained acceptable physical characteristics and sensorial acceptability, while in some cases an improvement is seen due to the effect of probiotics and prebiotics. The results obtained from several studies done, have shown the viability of developing functional bakery products by applying prebiotics or probiotics. This could be used as an encouragement for more research to be done in this topic.

Effect of ultrasound pre-treatment on the physicochemical composition of Agave durangensis leaves and potential enzyme production.

Approximately 1 million tons of agave plants are processed annually by the Mexican tequila and mezcal industry, generating vast amounts of agroindustrial solid waste. This type of lignocellulosic biomass is considered to be agroindustrial residue, which can be used to produce enzymes, giving it added value. However, the structure of lignocellulosic biomass makes it highly recalcitrant, and results in relatively low yield when used in its native form. The aim of this study was to investigate an effective pre-treatment method for the production of commercially important hydrolytic enzymes. In this work, the physical and chemical modification of Agave durangensis leaves was analysed using ultrasound and high temperature as pre-treatments, and production of enzymes was evaluated. The pre-treatments resulted in modification of the lignocellulosic structure and composition; the ultrasound pre-treatment improved the production of inulinase by 4 U/mg and cellulase by 0.297 U/mg, and thermal pre-treatment improved ß-fructofuranosidase by 30 U/mg.

Fermentation of Dietetic Fiber from Green Bean and Prickly Pear Shell by Pure and Mixture Culture of Lactobacillus acidophilus LA-5 and Bifidobacterium bifidum 450B.

The aim of this study was to evaluate the fermentation of dietary fiber from green bean (Phaseolus vulgaris) and prickly pear shell (Opuntia ficus-indica) by Lactobacillus acidophilus LA-5 and Bifidobacterium bifidum 450B growing as mono-culture and co-culture, the fermentation products, and proteins expressed during this process. The analysis of the fermentation profile showed a major growth of bacteria in the culture media of each dietary fiber supplemented with glucose, and particularly B. bifidum 450B at 48 h showed the highest growth. In the case of the co-culture, the growth was lower indicating the possible negative interaction between L. acidophilus LA-5 and B. bifidum 450B and may be due to the less amount of carbohydrates and the high content of non-soluble fiber that affected the nutrients availability for the bacterial strains. The pH changes indicated the presence of short-chain fatty acids (SCFAs), being acetate (46-100%) the main SCFA. Changes in the proteome concerned proteins that are involved in carbohydrate and other carbohydrate pathways. The characterization of the bacteria according to the growth, metabolites, and proteins expressed allows understanding the response to the change of environmental conditions and could be useful to understand L. acidophilus LA-5 and B. bifidum 450B strains' adaptation to specific applications.

Gallic acid and tannase accumulation during fungal solid state culture of a tannin-rich desert plant (Larrea tridentata Cov.).

Larrea tridentata (Sesse & Mocino ex DC.) Coville, also known as Larrea, gobernadora, chaparral, or creosote bush, is a shrubby plant which dominates some areas of the desert southwest in the United States and Northern Mexico and its use has not been exploited and standardized. In this study, gobernadora was studied to evaluate its potential use for support of solid state culture. Influence of two minimal media added with gobernadora powder as the sole carbon source and inducer of tannin-degrading enzymes was evaluated. Cultures were initially 70% moisture, had a pH of 5.5 and were inoculated with Aspergillus niger Aa-20 at 2 x 10(7) spores per gram of media. Analysis of pH, moisture, tannin uptake, gallic acid accumulation and tannase production were evaluated. Results indicated a high content of condensed (39.4%dm) and hydrolysable (22.8%dm) tannins. Invasion capacity of fungal growth was of 0.15 mmh(-1). Tannase production reached values of 1040 Ul(-1) at 43 h of culture. During the first 48 h of culture, the concentration of gallic acid accumulation was 0.33 gl(-1). Gobernadora is a potential source of gallic acid and tannase production by solid state culture; however, further optimization of the process is needed.

Purification and partial characterization of an acidic polygalacturonase from Aspergillus kawachii.

An endo-polygalacturonase, named PGI, was purified to homogeneity from the culture filtrate of Aspergillus kawachii IFO 4033 grown in a glucose-tryptone medium. The molecular mass of PGI was estimated to be 60 kDa by SDS-PAGE and 40 kDa by gel filtration on Sephacryl S-100. The isoelectric point was 3.55 as determined by isoelectic focusing. PGI exhibited binding properties to ConA-Sepharose suggesting that the protein is glycosylated. The N-terminal amino acid sequence was also determined as S-T-C-T-F-T-D-A-A-T-A-S-E-S-K. The remarkable property of PGI was its high activity in the pH range 2.0-3.0 towards soluble and insoluble substrates, while being inactive at pH 5.0. Enzyme stability at low pHs was markedly enhanced by different compounds, such as proteins, polysaccharides, simple sugars and the substrate pectin. PGI was very efficient to extract pectin from lemmon protopectin and to macerate carrot tissues at pH 2.0. These properties make PGI an interesting biocatalyst for industrial applications under highly acidic conditions.

Aspergillus kawachii produces an acidic pectin releasing enzyme activity.

A pectin-releasing (protopectinase, PPase) activity was found in a culture filtrate of Aspergillus kawachii IFO 4308. PPase activity was highest in the pH range of 2.0-2.5 and it was highly stable at 50 degrees C (85% of residual activity was found after a 10-h incubation in citrate-phosphate buffer, pH 3.0). Among other different enzyme activities, which are usually involved in plant cell-wall degradation, only polygalacturonase activity was detected. This result suggests that the PPase activity could correspond to a particular kind of polygalacturonase. Pectin extraction from lemon peels carried out at 50 degrees C for 2 h (pH 3.5) gave yields of ethanol-precipitated pectin equivalent to 17.4% of the initial total solids contained in the peels. Thus, this enzyme activity would allow carrying out a pectin extraction process at lower reaction pHs and higher temperatures in comparison with similar reports using other PPases. These properties seem to be very interesting from the practical point of view.

[Microbial and enzymatic extraction of pectin. A review]. / Revisión: extracción microbiológica y enzimática de pectina.

Great amounts of agroindustrial wastes rich in polysaccharides, such as pectic substances, are produced worldwide. Some of these wastes are used for the production of pectin. Currently, pectin is extracted at industrial scale by physicochemical means, but lately new biotechnological alternatives have been developed. In this review, the principal characteristics of pectic substances and pectic enzymes are described. The traditional physicochemical method for the pectin extraction is described and the new biotechnological (microbial and enzymatic) methods for pectin extraction are discussed and commented as well.