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El frijol común, Phaseolus vulgaris L. es un alimento importante por su aporte nutricional y nutraceútico. La aplicación de fertilizantes sintéticos es común para nutrir los suelos, y como consecuencia de sus efectos adversos, se han estudiado fuentes alternativas de fertilización. El pimiento morrón (Capsicum annuum) de desecho (PMD) posee nutrientes de interés, por lo que se puede utilizar para producir biofertilizantes. En esta investigación se produjo un biofertilizante a través de la fermentación del PMD con el hongo Aspergillus niger y se evaluó su aplicación (0 %, 50 %, 100 % y 200 %) sobre el desarrollo de plantas de Flor de junio León y Flor de Mayo Eugenia, los días 10 y 25. El diámetro de tallo es semejante entre los tratamientos y cultivares. El alto de la planta presenta resultados significativos en el cultivar flor Eugenia a 25 días, el largo de la hoja en el tratamiento de 100 %, y el ancho de hoja destaca en el cultivar flor de mayo Eugenia. El biofertilizante elaborado demuestra tener efectos significativos en los parámetros evaluados en el desarrollo de la planta de frijol.

Kosakonia cowanii strain Ch1 was isolated from Mexican chili powder, and the genome was sequenced. The genome was 4,765,544 bp in length, with an average G + C content of 56.22%, and a plasmid (pCh1) of 128,063 bp with an average G + C content of 52.50%. A phylogenetic analysis revealed a close relation with pathogenic strains; nevertheless, some virulence-related genes were absent, and this genetic characteristic may explain the fact that K. cowanii Ch1 behaved as a non-pathogenic strain when infection assays were performed on the leaves and fruits of Capsicum annuum L. Surprisingly, we observed that this bacterial strain had the ability to spread throughout serrano pepper seeds. Furthermore, K. cowanii Ch1 was evaluated for the production of volatile organic compounds (VOCs) against fungal pathogens, and the results showed that Alternaria alternata and Sclerotium rolfsii were inhibited in a radial mycelial growth assay by a mean rate of 70% and 64%, while Fusarium oxysporum was inhibited by only approximately 10%. Based on the headspace solid-phase microextraction combined with the gas chromatography mass spectrometry (HS-SPME-GC-MS), 67 potential VOCs were identified during the fermentation of K. cowanii Ch1 in TSA medium. From these VOCs, nine main compounds were identified based on relative peak area: dodecanoic acid; 3-hydroxy ethanol; 1-butanol-3-methyl; acetaldehyde; butanoic acid, butyl ester; cyclodecane; 2-butanone, 3-hydroxy; disulfide, dimethyl and pyrazine-2,5-dimethyl. Our findings show the potential of K. cowanii Ch1 for the biocontrol of fungal pathogens through VOCs production and reveal additional abilities and metabolic features as beneficial bacterial specie.

The use of waste in the manufacture of high-value products through biorefinery could lead to a circular bioeconomy. The objective of this work was to create combined cross-linked enzyme aggregates as an added-value product, the enzymes were produced through solid-state fermentation of paperboard residue for two days. The Trichoderma reesei crude extract had 1.6 and 1.3 times more amylase and xylanase activity than Aspergillus niger GS1, which in turn had 1.5-fold increase in cellulose 1,4-β-cellobiosidase activity over T. reesei. The enzimatic crude extract of T. reesei had increased activity at higher temperatures than A. niger GS1. Spray-dried combined cross-linking enzyme aggregates with enhanced hydrolytic activities were produced using fungal crude enzyme extracts. This process is proposed as a synergistic approach involving the generation of value-added products that could be used in biorefinery for bioethanol production from mango peels and the biowaste remediation leading to positive impacts in circular economy.

A comparison was made between a fixed aerobic biological process and a physicochemical treatment for waste effluents with butyl acetate. An acrylic tank with 100 L capacity and a support medium for PET bottles was implemented for the formation of the biofilm and thus develop the biological reactor. In the experimental phase, concentrations of 10, 20 and 30% of butyl acetate containing sample, using hydraulic retention times of: (16, 8, 5.33 and 4 days) for each concentration. After the experimentation, a removal of 99% of COD and 97% of BOD was obtained. For the physicochemical treatment, coagulant, flocculant, and adjuvants were used, by a jar test. A decrease in 74%, 53.8%, 55%, 97% and 37%, for electrical conductivity, total suspended solids, color, turbidity, COD and BOD respectively, were obtained compared to the initial sample. Both treatments were filtered through a bed packed with activated carbon, sand, and silica gravel. The aim of this work was to evaluate / quantify butyl acetate removal efficiency in each treatment for its subsequent comparison, with prospect to the reduction of similar pollutants in residual effluents is intended.

Castor bean (Ricinus communis) seeds contain ricinine, an alkaloid with insecticidal and insectistatic activities. Elicitation with salicylic acid (SA) has proven to stress R. communis and might modify the ricinine concentration. The aim of this study was to evaluate the concentration of ricinine in the bagasse of seeds from R. communis elicited with exogenous SA under greenhouse conditions. Plants were grown and divided into five groups, which were sprayed with SA and drench with 50 mL 60 days after sowing with concentrations of SA (0, 100, 300, 600 and 900 µM). Clusters were mixed and separated according to the treatment, and dried. The seeds were ground, the oil was extracted by Soxhlet with hexane, and then the bagasse was extracted with methanol. Ricinine was determined by HPLC. Elicitation did not change the plant height or diameter, the control group had 9.17 µg mL−1 of ricinine, and the concentrations followed a hormesis curve with the peak at 300 µM of SA that had a ricinine concentration of 18.25 µg mL−1. Elicitation with SA might be a cost-effective technique to increase ricinine from R. communis bagasse.

Corn pericarp (CP) results from wet milling of the corn industry. It is an abundant agro-industrial byproduct in Mexico, with potential use as sugars source to obtain ethanol and other economically relevant chemicals. In this work, CP was pretreated with dilute sulfuric acid at 121 °C; using a 23 full factorial design, factors were sulfuric acid, reaction time, and CP concentration. After pretreatment, the capacity of activated charcoal to remove inhibitory compounds in the liquid fraction was studied. Then, the detoxified liquid fraction was fermented using Scheffersomyces stipitis, whereas the solid fraction was exposed to enzymatic hydrolysis by a commercial cellulase (Cellic® CTec2). The most promising pretreatments utilized 2% (v/v) sulfuric acid, 20% (w/v) of CP, and 30 min reaction time producing 109.38 ± 6.73 g/L reducing sugars. The solid fraction obtained from CP pretreatment resulted in cellulose conversion up to 85.60% ± 1.87% after 94 h, significantly higher than conversion achieved using untreated CP of 32.54% ± 5.58%. The detoxification process allowed yeast fermentation to reach ethanol yields (g ethanol/g consumed substrate) between 0.09 ± 0.02 and 0.29 ± 0.006. S. stipitis was able to produce between 4.62 ± 1.73 and 14.22 ± 0.98 g/L of ethanol from the hydrolyzed liquid fraction. The dilute acid pretreatment on CP produced a solid fraction, which upon enzymatic treatment caused high cellulose conversion into reducing sugars. Additionally, the fermentability of the sugars present in the liquid fraction was increased after the detoxification process. Thus, CP is a material that shows good potential to obtain value-added products such as ethanol.

Air pollution is increasing globally, coupled with the downward trend in oil reserves. It is important to consider recent researches on renewable fuels such as bioethanol, bioturbosine, biodiesel, green-hydrogen (gH2), among others, as viable options to help reduce the impact of the use and consumption of fossil fuels. In this work is analyzed the Greenhouse Gases production (GHG) by combustion of binary and ternary mixtures, in a 5500 W portable engine generator of alternating current; connecting to the generator three electric charges as a dynamic brake. It were measured the decrements in the production of CO, HC and NOx of up to 99%, 93% and 67%, respectively, as well as an increment in CO2 up to 35%; in addition, reduction in uptake fuel of more than 36%. Therefore, the reduction of GHG emissions will improve the quality of air in the cities, at the same time the quality of people's health.

Active edible films and coatings incorporating antimicrobial agents such as essential oils are studied to improve the shelf-life of fresh foods. The aim of this work was to study a mixture of sodium caseinate-chitosan (SC:CH), added with mesoporous silica nanoparticles filled with oregano essential oil (MSN-OEO), to produce an active edible coating for Panela cheese and to evaluate its properties during refrigerated storage for 15 days. The OEO was extracted by hydrodistillation and was incorporated into the MSN. Films based on SC:CH of 4:1 and 8:1 ratios with and without MSN-OEO were produced and the mechanical, barrier, physicochemical and microbiological properties of the films were evaluated. The SC:CH 8:1 ratio (w/w) with MSN-OEO showed reduced mean particle size (764.8 ± 23.3 nm), and a stable solution (zeta potential = 29.9 ± 1.1 mV). The thickness and solubility were influenced by the incorporation of MSN-OEO making it thinner and less soluble. Panela cheese samples were coated by the spray method using the SC:CH 8:1 containing MSN-OEO film forming solution. The final pH of the control cheese was 0.5 units lower than that of the coated cheese, whereas final moisture loss of the control cheese was 4.2 times that of the coated cheese. The mesophilic aerobic bacteria and of molds and yeasts populations achieved a reduction of about 2 Log10 UFC/g after 15 days of storage. Due to microbial growth delay, and little moisture loss, this active coating may improve the quality and safety of Panela cheese.

Cross-linking of magnetic nanoparticles with proteins plays a significant role in the preparation of new materials for biotechnological applications. The aim was the maximization of the magnetic mass attracted and protein loading of magnetic iron oxide nanoparticles coated with chitosan, synthesized in a single step by alkaline precipitation. Chitosan-coated magnetite particles (Fe3O4@Chitosan) were cross-linked to a xylanase and a cellulase (Fe3O4@Chitosan@Proteins), showing a 93% of the magnetic saturation of the magnetite. X-ray diffraction pattern in composites corresponds to magnetite. Thermogravimetry and differential scanning calorimetry showed that 162 mg of chitosan was coating one gram of composite and 12 mg of protein was cross-linked to each gram of magnetic support. Cross-linking between enzymes and Fe3O4@Chitosan was confirmed by infrared spectroscopy with Fourier transform, X-ray energy, and X-ray photoelectron spectroscopy dispersion analysis. From dynamic light scattering, transmission and electron microscopy the average particle size distribution was 230 nm and 430 nm for Fe3O4@Chitosan and Fe3O4@Chitosan@Proteins, showing agglomerates of individual spherical particles, with an average diameter of 8.5 nm and 10.8 nm, respectively. The preparation method plays a key role in determining the particle size and shape, size distribution, surface chemistry, and, therefore, the applications of the superparamagnetic nanoparticles.

The aim of this work was the isolation of endophytic cacti fungi producer of pigments. Twenty different endophytic fungi were isolated from Ferocactus latispinus using a standard method. One of these was an orange pigment producer and was identified with molecular biology techniques amplifying internal transcribe spacer region. The fungus identified was Fusarium solani; it is a producer of polyketides from naphthoquinones family. Experiments with different carbon and nitrogen sources were performed, and it was found that both glycerol and ammonia sulphate promote the naphthoquinones biosynthesis. It was also found that the carbon/nitrogen ratio and pH value had an effect on this biosynthesis phenomenon; increasing productivity being observed at the initial C: N ratio of 59.6, pH 6 and time of 113.3 h. This C: N ratio exhibited a stress condition for fungi in the pigment biosynthesis process in liquid media. The optimum value of total naphthoquinones (476 μmol/L) was obtained using a central rotable composite design.

Corn pericarp (CP) is an inexpensive agroindustrial by-product that is available in large quantity in Mexico. This work aimed to optimize the use of a dilute sulfuric acid pretreatment for CP hydrolysis to maximize the reducing sugars yield. A 2-step experimental design was used, first a full factorial followed by a central composite design (CCD). The CCD involved sulfuric acid (1.5% to 5%, v/v), a treatment at 121 ºC (15 min to 40 min), and varying CP content (10% to 20%, w/v). The response variables were the reducing sugars, glucose, and solubilized solids. Maximal responses were achieved at 3.4% (v/v) sulfuric acid, 20% (w/v) CP, and 22.3 min. A significant (R2 = 0.99) second-order model predicted maximal operational conditions that were experimentally validated: 80.1 g/L reducing sugars, 12.8 g/L glucose, and 69.2% solubilization of CP solids. The dilute sulfuric acid pretreatment solubilized all hemicellulose in CP.

The growing demand for minimally processed foods with a long shelf life and environmentally friendly materials has forced industry to develop new technologies for food preservation and handling. The use of edible films has emerged as an alternative solution to this problem, and mixtures of carbohydrates and proteins, may be formulated to improve their properties. The objective of this work was to evaluate the effect of protein cross-linking with transglutaminase (TG) of two varieties of quinoa protein isolate (Chenopodium quinoa) [Willd (QW), and Pasankalla (QP)] on the physicochemical and barrier properties of edible films based on chitosan (CT)-quinoa protein. The evaluated properties were water vapor permeability (WVP), solubility, adsorption, roughness determined by atomic force microscopy, and the interactions among the main film components determined by Raman spectroscopy. The results indicated that TG interacted with lysine of QW and QP. CT:QW (1:5, w/w) showed the lowest solubility (14.02 &plusmn, 2.17% w/w). WVP varied with the composition of the mixture. The WVP of CT:quinoa protein ranged from 2.85 to 9.95 &times, 10&minus, 11 g cm Pa&minus, 1 cm&minus, 2 s&minus, 1 without TG, whereas adding TG reduced this range to 2.42&ndash, 4.69 &times, 1. The addition of TG to CT:QP (1:10, w/w) reduced the film surface roughness from 8.0 &plusmn, 0.5 nm to 4.4 &plusmn, 0.3 nm. According to the sorption isotherm, the addition of TG to CT-QW films improved their stability [monolayer (Xm) = 0.13 &plusmn, 0.02 %]. Films with a higher amount of cross-linking showed the highest improvement in the evaluated physical properties, but interactions among proteins that were catalyzed by TG depended on the protein source and profile.

Enzyme immobilization on different supports has emerged as an efficient and cost-effective tool to improve their stability and reuse capacity. This work aimed to produce a stable immobilized multienzymatic system of xylanase and filter paper-ase (FPase) onto magnetic chitosan using genipin as a cross-linking agent and to evaluate its biochemical properties and reuse capacity. A mixture of chitosan magnetic nanoparticles, xylanase, and FPase was covalently bonded using genipin. Immobilization yield and efficiency were quantified. The activity of free and immobilized enzymes was quantified at different values of pH, temperature, substrate concentration (Km and Vmax), and reuse cycles. The immobilization yield, immobilization efficiency, and activity recovery were 145.3% ± 3.06%, 14.8% ± 0.81%, and 21.5% ± 0.72%, respectively, measured as the total hydrolytic activity. Immobilization confers resistance to acidic/basic conditions and thermal stability compared to the free form. Immobilization improved 3.5-fold and 78-fold the catalytic efficiency (Kcat/Km) of the xylanase and filter paper-ase activities, while immobilized xylanase and FPase could be reused for 34 min and 43 min, respectively. Cross-linking significantly improved the biochemical properties of immobilized enzymes, combined with their simplicity of reuse due to the paramagnetic property of the support. Multienzyme immobilization technology is an important issue for industrial applications.

Solid state fermentation (SSF) is used to produce industrial enzymes. The objective of this study was to use a co-culture of Aspergillus niger GS1 and Trichoderma reesei, grown on a mixture of Bermuda grass and corn cob to obtain fermented forage (FF) rich in hydrolytic enzymes, as a value added ingredient for animal feed. FPase, amylase and xylanase productivities (dry matter, DM) were 8.8, 181.4, and 42.1Ug(-1)h(-1), respectively (1U=reducing sugars released min(-1)), after 12-16h of SSF with C/N=60. Cellulose, hemicellulose and lignin decreased 1.6-, 2.7- and 1.9-fold (DM), respectively. In vitro ruminal and true digestibility of DM was improved 2.4- and 1.4-fold. Ruminal digestion of FF reduced 1.32-fold the acetate:propionate ratio, which may reduce the environmental impact of ruminants feeding. On-site hydrolytic enzymes productivity using SSF without enzymes extraction could be of economic potential for digestibility improvement in animal feed.

The effectiveness of edible films (EFs) used as coatings to maintain the quality and safety of fresh produce for long time depends on their functional properties characterization. This study was aimed to design and evaluate physicochemical, barrier, mechanical, and antimicrobial properties of EFs based on corn starch (acetylated cross-linked (ACLS) or oxidized (OS)), micro-emulsified beeswax (BW, 0-1 % w/w), and two natural antimicrobials (lauric arginate (LAE, 400-4000 mg/L) and natamycin (NAT, 80-800 mg/L)). EFs based on ACLS or OS made with 1 % BW microemulsion produced homogeneous EFs surface and did not show changes in thickness or opacity. Water vapor permeability (WVP, 0.57 ± 0.04 g mm m−2 h−1 kPa−1 for ACLS, and 0.56 ± 0.05 g mm m−2 h−1 kPa−1 for OS) was reduced; tensile strength (TS, 51.48 ± 5.92 MPa for ACLS, and 40.96 ± 4.98 MPa for OS), and elastic modulus (EM, 211.30 ± 7.85 MPa for ACLS, and 203.50 ± 5.35 MPa for OS) were decreased, whereas elongation at break (E, 4.59 ± 1.11 % for ACLS, and 4.76 ± 4.98 % for OS) increased. The additive effect showed by the combination of natural antimicrobials (2000 mg/L of LAE plus 400 mg/L of NAT) incorporated into EFs with 1 % BW completely inhibited Rhizopus stolonifer, Colletotrichum gloeosporioides, Botrytis cinerea, and Salmonella Saintpaul. These properties of corn starch EFs used as coatings represent an excellent alternative to extend the shelf life of fresh produce. We are grateful to CONACyT for PhD grant to Teresita Arredondo Ochoa, and financial support for project No. 166751.

There is growing interest in developing high-yield and low-cost production of xylanolytic enzymes for industrial applications using agroindustrial byproducts. A native strain of Aspergillus niger GS1 was used to produce β-xylosidase (EC 3.2.1.37) on solid state fermentation using corn pericarp (CP) with innovative alkaline electrolyzed water (AEW) pretreatment at room temperature. β-xylosidase was purified by ammonium sulfate fractionation followed by anion exchange and hydrophobic interaction chromatographies. β-Xylosidase showed a molecular weight of 111 kDa, isoelectric point of 5.35 and specific activity of 386.7 U (mg protein)−1, using p-nitrophenyl-β- d -xylopyranoside as substrate, at pH 5 and 60 °C, and optimal activity at pH 4.5. Optimal temperature was 65 °C, showing full activity after 1 h at 60 °C. Activity was reduced by 1 mM β-mercaptoethanol (55.6 ± 0.1%), and enhanced by 1 mM SDS (11.0 ± 0.03%). Km and Vmax were 6.1 ± 0.9 mM and 1364 ± 105 U (mg protein)−1, respectively, whereas kcat was 5.1 s−1. A predominant α-helix (41%) was determined from circular dichroism on β-xylosidase, while thermal transition profiles produced a Tm of 54.1 ± 5.8 °C, enthalpy change for unfolding of 67.4 ± 6.7 kJ/mol, and onset temperature of 37 °C. Pre-treatment of CP using AEW is an ecologically friendly alternative to chemical and heat treatments for the production of relatively high levels of β-xylosidase.

Papaya production plays an important economic role in Mexico&rsquo, s economy. After harvest, it continues to ripen, leading to softening, skin color changes, development of strong aroma, and microbial spoilage. The objective of this work was to apply an active coating of chitosan&ndash, starch to increase papaya shelf life and to evaluate physicochemical and antimicrobial properties of the coating. Papaya surfaces were coated with a chitosan-oxidized starch (1:3 w/w) solution and stored at room temperature (25 &plusmn, 1 &deg, C) for 15 days. Variables measured were color, titratable acidity, vitamin C, pH, soluble solids, volatile compounds by gas chromatography, texture, homogeneity by image analysis, and coating antimicrobial activity. At the end of the storage time, there were no significant differences (p &gt, 0.05) between coated and uncoated papayas for pH (4.3 &plusmn, 0.2), titratable acidity (0.12% &plusmn, 0.01% citric acid), and soluble solids (12 &plusmn, 0.2 &deg, Bx). Papaya firmness decreased to 10 N for coated and 0.5 N for uncoated papayas. Volatile compounds identified in uncoated papaya (acetic acid, butyric acid, ethyl acetate, ethyl butanoate) are related to fermentation. Total microbial population of coated papaya decreased after 15 days, whereas population of uncoated papaya increased. This active coating permitted longer shelf life of papaya than that of the uncoated fruit.

This paper reports on the optimum concentrations of naphthalene acetic acid (NAA) and 6-benzyladenine (BA) to stimulate callus growth and NAA; kinetin and silver nitrate (AgNO3) for callus redifferentiation in Dianthus caryophyllus L. Meristems were excised and placed in MS medium with 30 g l−1 sucrose and 9.0 μM 2,4-d. Callus clusters were transferred to MS medium containing NAA (0, 1.7, 3.3, and 5.0 μM) and BA (0, 1.7, 3.3, and 5.0 μM) for proliferation and to MS medium with 30 g l−1 sucrose, 2.5 g l−1 phytagel, kinetin (0, 33, and 66 μM); NAA (0, 7.95, and 15.9 μM) and AgNO3 (0, 23.54 and 47.08 μM) for shoot and root induction. Treatments were applied according to a Box–Behnken design. After callus growth and redifferentiation, plants were incubated in the greenhouse at 18 ± 2°C for 4 wk and at 20–26°C for 4 wk. Finally, plants were changed to near-commercial greenhouse conditions with different day (30–35°C) and night (16–24°C) temperatures. Results showed better callus growth at higher NAA concentrations. A maximum callus weight was found with 5.0 μM NAA but without BA. A maximum of 78% calluses with shoots was obtained with 15.9 μM NAA, 47.08 μM AgNO3, and 0.74 μM kinetin and 58% with roots with 15.7 μM NAA and 47.08 μM AgNO3, but without kinetin. The shoots obtained showed little hyperhydricity. Vigorous plants were obtained after gradual acclimatization with an 80% survival rate under nursery conditions.

Animal origin foods are widely distributed and consumed around the world due to their high nutrients availability but may also provide a suitable environment for growth of pathogenic and spoilage microorganisms. Nowadays consumers demand high quality food with an extended shelf life without chemical additives. Edible films and coatings (EFC) added with natural antimicrobials are a promising preservation technology for raw and processed meats because they provide good barrier against spoilage and pathogenic microorganisms. This review gathers updated research reported over the last ten years related to antimicrobial EFC applied to meat and meat products. In addition, the films gas barrier properties contribute to extended shelf life because physicochemical changes, such as color, texture, and moisture, may be significantly minimized. The effectiveness showed by different types of antimicrobial EFC depends on meat source, polymer used, film barrier properties, target microorganism, antimicrobial substance properties, and storage conditions. The perspective of this technology includes tailoring of coating procedures to meet industry requirements and shelf life increase of meat and meat products to ensure quality and safety without changes in sensory characteristics.

Hemicellulosic agricultural by-products such as corn stover (CS) are highly available materials which represent an opportunity to develop value added products. Native Aspergillus niger GS1 was used for solid-state fermentation (SSF) on alkali pre-treated CS (ACS) aimed to optimize xylanolytic enzymes production, and their effect on in vitro ruminal and true digestibility of ACS. Enzyme production was empirically modelled using a fractional factorial design 2 9-5 , and the resulting significant factors were glucose, yeast extract and two mineral salts, which were arranged in a Draper-Lin optimization design at two levels. Predicted optimum xylanolytic activity of 33.6 U (mg protein) -1 was achieved at 48 hrs of SSF, and was validated by confirmatory experiments. ACS was incubated with a semipurified enzymatic extract (EE) showing a xylanolytic activity of 1600 U kg -1 dry ACS for 12 hrs before exposure to cow's ruminal liquid for 72 hrs, which led to 5% and 10% increase of in vitro ruminal and true digestibility, respectively. CS is a readily available by-product in different regions which after alkaline treatment and partial hydrolysis with the EE, may be advantageously used as supplement for ruminant feed.

Xylan constitutes the second most abundant source of renewable organic carbon on earth and is located in the cell walls of hardwood and softwood plants in the form of hemicellulose. Based on its availability, there is a growing interest in production of xylanolytic enzymes for industrial applications. β-1,4-xylan xylosidase (EC 3.2.1.37) hydrolyses from the nonreducing end of xylooligosaccharides arising from endo-1,4-β-xylanase activity. This work reports the partial characterization of a purified β-xylosidase from the native strain Aspergillus niger GS1 expressed by means of a fungal system. A gene encoding β-xylosidase, xlnD, was successfully cloned from a native A. niger GS1 strain. The recombinant enzyme was expressed in A. niger AB4.1 under control of A. nidulans gpdA promoter and trpC terminator. β-xylosidase was purified by affinity chromatography, with an apparent molecular weight of 90 kDa, and showed a maximum activity of 4,280 U mg protein(-1) at 70°C, pH 3.6. Half-life was 74 min at 70°C, activation energy was 58.9 kJ mol(-1), and at 50°C optimum stability was shown at pH 4.0-5.0. β-xylosidase kept residual activity83% in the presence of dithiothreitol (DTT), β-mercaptoethanol, sodium dodecyl sulfate (SDS), ethylenediaminetetraacetate (EDTA), and Zn(2+). Production of a hemicellulolytic free xylosidase showed some advantages in applications, such as animal feed, enzymatic synthesis, and the fruit-juice industry where the presence of certain compounds, high temperatures, and acid media is unavoidable in the juice-making process.

The xyn5 gene, which encodes an endo-β-1,4-xylanase (Xyn5), in Aspergillus niger GS1 was cloned into an expression cassette under the control of constitutive glyceraldhehyde-3-phosphate dehydrogenase gene promoter. The expression system was designed to produce the recombinant enzyme containing a six-histidine peptide fused to the carboxyl end of the protein. The efficiency of Xyn5 production under submerged (SmF) and solid-state (SSF) fermentation was investigated using the homologous cotransformed A. niger AB4.1. A productivity of 17.1 U/(l·h) was estimated for SSF and 3.2 U/(l·h) for SmF calculated at peak value of enzyme titers. Recombinant Xyn5 obtained by SSF on polyurethane fiber, was purified 5.1-fold by anion exchange and immobilized metal affinity chromatography, with 35.7% recovery. The purified recombinant enzyme showed an apparent molecular weight of 30 kDa and optimal activity (522 U/mg protein) at pH 5.5 and 50°C.Key words: Aspergillus niger GS1, xylanolytic activity, solid-state fermentation, homologue expression, polyurethane fiber.