Creating a novel genetic diversity of Trichoderma afroharzianum by γ-radiation for xylanase-cellulase production

Creating novel sources of a microbial strain using induced mutation can increase enzyme production for industrial use. According to this, we have developed a mutant strain of Trichoderma afroharzianum by Co60 gamma irradiation. Trichoderma mutants were isolated from an optimum dose of 250 Gy. The qualitative and quantitative screening were used for evaluating their enzyme production and the DNA barcoding method was used to identify the best Trichoderma mutant isolates. The highest cellulase (exo-glucanase, endoglucanase, β-glucosidase, and total cellulase) and xylanase activities were observed in superior mutant isolates of Trichoderma afroharzianum NAS107-M44 and Trichoderma afroharzianum NAS107-M82, which is approximately 1.6-2.5 times higher than its parent strain, respectively. The electrophoretic pattern of proteins showed that the exo-glucanase I, endo-glucanase III, and the xylanase I enzymes hydrolyzed the corn bran, synergistically. Overall, gamma irradiation-induced mutation could be an expedient technique to access such superior mutants for the bioconversion of corn bran wastes.

Improvement of the functional properties of insoluble dietary fiber from corn bran by ultrasonic-microwave synergistic modification

A comprehensive investigation aimed to access the impacts of ultrasonic, microwave, and ultrasonic-microwave synergistic modification on the physicochemical properties, microstructure, and functional properties of corn bran insoluble dietary fiber (CBIDF). Our findings revealed that CBIDF presented a porous structure with loose folds, and the particle size and relative crystallinity were slightly decreased after modification. The CBIDF, which was modified by ultrasound-microwave synergistic treatment, exhibited remarkable benefits in terms of its adsorption capacity, and cholate adsorption capacity. Furthermore, the modification improved the in vitro hypoglycemic activity of the CBIDF by enhancing glucose absorption, retarding the starch hydrolysis, and facilitating the diffusion of glucose solution. The findings from the in vitro probiotic activity indicate that ultrasound-microwave synergistic modification also enhances the growth-promoting ability and adsorbability of Lactobacillus acidophilus and Bifidobacterium longum. Additionally, the level of soluble dietary fiber was found to be positively correlated with CBIDF adsorbability, while the crystallinity of CBIDF showed a negative correlation with α-glucosidase and α-amylase inhibition activity, as well as water-holding capacity, and oil-holding capacity.

Conformational properties of heterogeneous arabinoxylan protein gums from corn bran and distillers grains in comparison with gum arabic

The molecular structure and conformation of arabinoxylan-protein gum, commonly referred as corn fiber gum (CFG) were analyzed by high-performance size-exclusion chromatography (HPSEC) coupled with RI, UV, light scattering and viscometer detectors. CFG had a heterogeneous structure. The detailed conformation of CFG at different molecular weights was compared with that of hemicellulose fiber gum (HFG) from dried distiller's grains with solubles and gum arabic. The CFG molecules mainly had random coil conformation; only 10 % of them exhibited rigid rod conformation. Approximately 80 % of the CFG had a molecular weight between 105 and 105.4 Da, while the other 20 % of molecules were between 105.4 and 1.5 × 107.7 Da. The overall conformational properties of CFG and HFG were closer but differed from that of gum arabic. The intrinsic viscosity and radius of gyration of both CFG and HFG were greater than those of gum arabic although the average molecular weight of CFG and HFG was lower. The protein and carbohydrate were covalently linked in CFG molecules as shown by the HPSEC-multiple detectors combined with partial acid hydrolysis. Based on the detailed conformation of CFG and the methylation analysis, 1D and 2D NMR spectroscopy results, the molecular structure of CFG was proposed.

Structural and emulsion-stabilizing properties of the alkali-extracted arabinoxylans from corn and wheat brans

This study investigated the structural and emulsion-stabilizing capacities of alkali-extracted arabinoxylans from corn and wheat bran (CAXs and WAXs). The results demonstrated that all AXs were mainly composed of arabinose and xylose. WAXs had a higher weight-average molecular weight (Mw, 375-473 KDa) and protein content (3.09-8.68 %) but lower total phenolic acid content (TPC, 1.18-1.91 mg gallic acid equivalents/g) than CAXs; however, CAX stabilized emulsions exhibited smaller and more regular oil droplet size (524-589 nm) and higher absolute value of ζ potential (48-52 mV) compared with WAX stabilized emulsions during storage. Moreover, the increment of NaOH concentration caused a decrease in Mw, protein content, and TPC of CAXs or WAXs and the corresponding CAXs or WAXs emulsions showed bigger and more unstable oil droplets during 14 d storage. The Mw, protein, and TPC were well correlated with their emulsion stability. Furthermore, emulsions stabilized by AXs with low-concentration NaOH could resist better various temperatures, pH, and NaCl. In conclusion, the structural properties of AXs derived from different cereal sources and treated with different concentrations of NaOH varied, leading to differences in their ability to stabilize emulsions. CAXs or WAXs obtained from low-concentration NaOH treatment demonstrated significant potential as highly effective natural emulsifiers.

Expression and characterization of α-L-arabinofuranosidase derived from Aspergillus awamori and its enzymatic degradation of corn byproducts with xylanase

In this study, α-L-arabinofuranosidase (AF) from Aspergillus awamori was heterologously expressed in Pichia pastoris X33, with a 1-fold increase in AF activity after codon and vector optimization. AF remained stable at 60-65 °C and displayed a broad pH stability range of 2.5-8.0. It also demonstrated considerable resistance to pepsin and trypsin. Furthermore, compared with xylanase alone, AF with xylanase exhibited a marked synergistic effect in the degradation of expanded corn bran, corn bran, and corn distillers' dried grains with solubles, reducing sugars by 3.6-fold, 1.4-fold, and 6.5-fold, respectively, with the degree of synergy increasing to 4.61, 2.44, and 5.4, respectively, while in vitro dry matter digestibility values were 17.6%, 5.2%, and 8.8%, respectively. After enzymatic saccharification, corn byproducts were converted to prebiotic xylo-oligosaccharides and arabinoses, thereby demonstrating the favorable properties of AF in the degradation of corn biomass and its byproducts.

Production of β-glucan exopolysaccharide lasiodiplodan by Lasiodiplodia theobromae CCT 3966 from corn bran acid hydrolysate

The potential utilization of corn bran acid hydrolysate (CBAH) was evaluated as an inexpensive feedstock for the production of a rich carbohydrate and protein medium for lasiodiplodan (LAS) production using the filamentous fungus Lasiodiplodia theobromae CCT 3966. Experiments were performed according to a 2² CCRD experimental design aiming to evaluate the influence of agitation speed (rpm) and temperature (°C) over the production of total cell biomass (TCB) and LAS concentration released to the medium (LAS-M), adhered to biomass (LAS-C), and total (LAS-T). Under the selected conditions (temperature of 28°C and agitation of 200 rpm), 8.73 g·L^-1 of LAS-T and 4.47 g·L^-1 of TCB were obtained. Recovery of LAS-C with hot water was shown as an alternative to increase the production concentration, although it might require further purification steps. CBAH potential for substitution of synthetic media was demonstrated, indicating that it is an adequate raw material containing all necessary nutrients for LAS production.Key points• Corn bran acid hydrolysate is presented as a suitable substrate for β-glucan production.• Lasiodiplodia theobromae CCT 3966 have the potential for the industrial β-glucan production.• Simple recovering of biomass-adhered lasiodiplodan by hot water extraction.

Production and statistical optimization of Paromomycin by Streptomyces rimosus NRRL 2455 in solid state fermentation

BACKGROUND

Paromomycin is a 2-deoxystreptamine aminocyclitol aminoglycoside antibiotic with broad spectrum activity against Gram-negative, Gram-positive bacteria and many protozoa. This study introduces a strategy for paromomycin production through solid-state fermentation using Streptomyces rimosus subsp. paromomycinus NRRL 2455. Solid state fermentation has gained enormous attention in the development of several products because of their numerous advantages over submerged liquid fermentation. After selecting the best solid substrate, a time course study of paromomycin production was carried out followed by optimization of environmental conditions using response surface methodology. Paromomycin yields obtained using this technique were also compared to those obtained using submerged liquid fermentation.

RESULTS

Upon screening of 6 different substrates, maximum paromomycin concentration (0.51 mg/g initial dry solids) was obtained with the cost-effective agro-industrial byproduct, corn bran, impregnated with aminoglycoside production media. Optimization of environmental conditions using D-optimal design yielded a 4.3-fold enhancement in paromomycin concentration reaching 2.21 mg/g initial dry solids at a pH of 8.5, inoculum size of 5% v/w and a temperature of 30 °C.

CONCLUSION

Compared to submerged liquid fermentation, solid state fermentation resulted in comparable paromomycin concentrations, cost reduction of raw materials, less energy consumption and waste water discharge, which have major implications in industrial fermentation. Therefore, solid state fermentation is a promising alternative to submerged liquid fermentation for paromomycin production. To the best of our knowledge, this is the first report on the optimized paromomycin production through solid state fermentation process.

Development of high-fiber wheat bread using microfluidized corn bran

Microfluidized corn bran is an excellent source of dietary fiber but has not been used to develop high-fiber bread. To develop such bread, it replaced 18, 20, and 22% of flour in the control white bread formula. At the standard water content, the amount of water required to develop a dough consistency of 500 Brabender Units in farinograph tests, the resulting bread had worse microstructure and textural properties, and much smaller loaf volume than the control bread. Instead of using existing physical, chemical and enzymatic methods to reduce the deteriorating effects of bran, we resolved the issue effectively by optimizing the water content in bread formulas. For the three levels of bran addition, when the water content was increased from its standard values of 38.3, 38.6, 38.8% to 40.8, 41.9, and 44.0%, respectively, the obtained loaves exhibited similar microstructure, specific loaf volume, and textural properties to the control bread.

Response surface optimization of solid state fermentation for inulinase production from Penicillium oxalicum using corn bran

Response surface methodology has been implemented for the utilization of corn bran for inulinase production by Penicillium oxalicum. CCRD of RSM with 15 runs was practiced to optimize three independent variables: moisture (70-90%), incubation time (4-8 days) and pH (5-8). However, other media constituents viz. inulin (1%), NaNO3 (0.2%), NH4H2PO4 (0.2%), KH2PO4 (0.2%), MgSO4·7H2O (0.05%) and FeSO4·7H2O (0.001%) were kept constant during solid state fermentations. Solid state fermentations were carried out at 30 °C at flask-level. A substantial inulinase production (77.95 IU/gds) was obtained under the optimized conditions i.e., moisture (80%), incubation time (6.0 days) and pH (6.5). Multiple correlation coefficient 'R2' for inulinase production was 1.00, which justifies good agreement between experimental and predicted values. Besides, 'R2' value close to one, also authenticates the validity of the model. The experimentation carried out at laboratory scale shown corn bran a good substrate for inulinase production by P. oxalicum.

Corn bran bioprocessing: Development of an integrated process for microbial lipids production

This study investigated the potential of corn bran as a feedstock for microbial lipid production using oleaginous yeast, Trichosporon oleaginosus ATCC20509. Different conditions (solid loading of biomass, acid loading, and pretreatment duration) were applied to optimize pretreatment processes using the Box-Behnken design. The highest sugar yield of 0.53g/g was obtained from corn bran hydrolysates at a pretreatment condition of 5% solid loading and 1% acid loading for 30min. Compared with synthetic media, up to 50% higher lipid accumulations in T. oleaginosus were achieved using corn bran hydrolysates during fermentation. Also, the direct effect of pretreatment condition on the lipid accumulation of T. oleaginosus was investigated using response surface methodology (RSM). Solid loading of biomass during the pretreatment process significantly affected the fermentation process for lipid accumulation of T. oleaginosus. The RSM model can provide useful information to design an integrated bioconversion platform.

Enzymo-chemical preparation, physico-chemical characterization and hypolipidemic activity of granular corn bran dietary fibre

Corn bran dietary fibre (CF) was paid more attention for its anticancer and hypolipidemic activities. In this paper, corn bran was firstly decomposed to the threadlike fibre (CF1) by multiple enzymes and then further modified to the granular fibre (CF2) by alkali under high pressure and high temperature (APT). The two types of fibres were characterized by scanning electron microscope (SEM) and near-infrared spectrophotometer (IR), and investigated by hydration measurements and nitrite adsorption assays. The results showed that CF2 had more much specific surface area, and displayed 4.7, 6.3 and 30-fold increases in water retention (WR), swelling capacity (SC) and nitrite absorption (NA), compared with CF1, respectively. The rat feeding trials showed that the granular fibre could decrease total cholesterol (TC), triglyceride (TG) and low density lipoprotein-cholesterol (LDLC) by 41.4 %, 20.7 % and 56.5 %, respectively. These excellent physiological activities indicate that CF2 will be a potentially available dietary ingredient in functional food industries, and meanwile imply that the enzymochemical method is a desired strategy for CF processing.

Optimization of phytase production by Penicillium purpurogenum GE1 under solid state fermentation by using Box-Behnken design

Phytase production by Penicillium purpurogenum GE1 isolated from soil around bean root nodules was investigated by solid state fermentation (SSF) using mixed substrates consisted of corn cob and corn bran. The SSF conditions were optimized by using one-variable-at-a-time strategy. The optimum conditions for phytase production were at 27 °C, pH 8 and 66% moisture content. The study of different carbon and nitrogen sources revealed that glucose and peptone registered the highest enzyme productivity (92 ± 5.6 U/g ds, 125 ± 4.9 U/g ds). Among different surfactants, maximum phytase productivity was observed with Tween 80 at 0.001 concentrations (170 ± 4.2 U/g ds). A Box-Behnken design was employed to investigate the optimization of the most significant variables affecting the enzyme production. Maximal phytase production was detected after the addition of (g/5 g ds): 0.75 glucose, 0.375 peptone and 0, 01 tween 80. This result represented an improvement in phytase production of 2.6 folds when compared to that previously obtained using the basal medium under the same cultivation conditions. The generated model was found to be very adequate for phytase production (90% accuracy) as the experimental value was 444 ± 3.5 U/g ds compared to 401 U/g ds for the predicted value. In brief, the production of phytase using corn cob and corn bran is a novel and cheap way for the production of this important enzyme and opens a new way for researchers to discover and explore this arena.

Effect of incorporation of corn byproducts on quality of baked and extruded products from wheat flour and semolina

The effect of blending level (0, 5, 10, 15 and 20%) of corn bran, defatted germ and gluten with wheat flour on the physico-chemical properties (protein, crude fiber, phosphorus, iron and calcium), baking properties of bread, muffins and cookies, and extrusion properties of noodles and extruded snacks prepared from semolina were examined. Blending of wheat flour and corn byproducts significantly increased the protein, crude fiber, phosphorus, iron and calcium contents. Breads from gluten blends had higher loaf volume as compared to bran and germ breads. Among corn byproducts, gluten cookies were rated superior with respect to top grain. Muffins from germ blends and gluten blends had higher acceptability scores than the bran muffins. Blending of corn bran, defatted germ and gluten at 5 and 10% with wheat flour resulted in satisfactory bread, cookie, and muffin score. Quality of noodles was significantly influenced by addition of corn byproducts and their levels. Corn byproducts blending had significant influence on cooking time, however, gruel solid loss affected non-significantly in case of noodles. Expansion ratio and density of extruded snacks was affected non significantly by blending source and blending level. However, significant effect was observed on amperage, pressure, yield and overall acceptability of extruded snacks. Acceptable extruded products (noodles and extruded snacks) could be produced by blending corn byproducts with semolina upto 10% level.