High level phytase production by Aspergillus niger NCIM 563 in solid state culture: response surface optimization, up-scaling, and its partial characterization

Review on Desirable Microbial Phytases as a Poultry Feed Additive: Their Sources, Production, Enzymatic Evaluation, Market Size, and Regulation

Poultry's digestive tract lacks hydrolytic phytase enzymes, which results in chelation of dietary minerals, vital amino acids, proteins, and carbohydrates, phytate-phosphate unavailability, and contamination of the environment due to phosphorus. Therefore, it is necessary to use exogenous microbial phytases as feed additive to chicken feed to catalyze the hydrolysis of dietary phytate. Potential sources of microbial isolates that produce desired phytases for chicken feed supplementation have been isolated from agricultural croplands. It is achievable to isolate phytase-producing bacteria isolates using both broth and agar phytase screening media. Potential substrates for submerged fermentation (SmF) for bacterial phytase production and solid-state fermentation (SSF) for fungal phytase production include rice and wheat bran. Following fermentation, saturated ammonium sulphate precipitation is typically used to partially purify microbial culture filtrate. The precipitate is then desalted. Measurements of the pH optimum and stability, temperature optimum and stability, metal ions stability, specificity and affinity to target substrate, proteolysis resistance, storage stability, and in vitro feed dephosphorylation are used to perform an enzymatic evaluation of phytase as an additive for poultry feed. The growth of the feed phytase market is primarily due to the expansion of chicken farms to meet the demand for meat and eggs from humans. The Food and Drug Administration in the USA and the European Food and Safety Authority are primarily in charge of putting rules pertaining to feed phytase use in chicken feed into effect. Conclusively, important components of the production of phytase additives for poultry feed include identifying a reliable source for potential microbe isolation, selecting an economical method of phytase production, thoroughly characterizing the biochemical properties of phytase, and comprehending the size and regulation of the current feed phytase market.

Production of fungal phytases in solid state fermentation and potential biotechnological applications

Phytases are important enzymes used for eliminating the anti-nutritional properties of phytic acid in food and feed ingredients. Phytic acid is major form of organic phosphorus stored during seed setting. Monogastric animals cannot utilize this phytate-phosphorus due to lack of necessary enzymes. Therefore, phytic acid excretion is responsible for mineral deficiency and phosphorus pollution. Phytases have been reported from diverse microorganisms, however, fungal phytases are preferred due to their unique properties. Aspergillus species are the predominant producers of phytases and have been explored widely as compared to other fungi. Solid-state fermentation has been studied as an economical process for the production of phytases to utilize various agro-industrial residues. Mixed substrate fermentation has also been reported for the production of phytases. Physical and chemical parameters including pH, temperature, and concentrations of media components have significantly affected the production of phytases in solid state fermentation. Fungi produced high levels of phytases in solid state fermentation utilizing economical substrates. Optimization of culture conditions using different approaches has significantly improved the production of phytases. Fungal phytases are histidine acid phosphatases exhibiting broad substrate specificity, are relatively thermostable and protease-resistant. These phytases have been found effective in dephytinization of food and feed samples with concomitant liberation of minerals, sugars and soluble proteins. Additionally, they have improved the growth of plants by increasing the availability of phosphorus and other minerals. Furthermore, phytases from fungi have played an important roles in bread making, semi-synthesis of peroxidase, biofuel production, production of myo-inositol phosphates and management of environmental pollution. This review article describes the production of fungal phytases in solid state fermentation and their biotechnological applications.

Bioinformatic Studies, Experimental Validation of Phytase Production and Optimization of Fermentation Conditions for Enhancing Phytase Enzyme Production by Different Microorganisms under Solid-State Fermentation

Background:

Phytase is an essential enzyme necessary for the digestive process. It is a natural enzyme found in plant materials. It prevents bad effect of phytic acid on protein and energy utilization. Phytase frees the bound minerals such as phosphorus, calcium, zinc, iron, magnesium and manganese from the phytic acid molecule providing essential minerals available for healthy nutrition. This study depends on converting food processing waste into highly valuable products. Optimizing the fermentation conditions for enhancing high phytase production with low cost was the objective of this research.

Methods:

A bibliographical survey was carried out to select the most fungul producers of phytase from fungal species deposited in NCBI database. Phytases of the selected organisms were analyzed in the UNIPROT database and their protein sequences were submitted to multiple sequence alignments using Clustal Omega and visualized using Jalview program. Experimental studies using five fungal strains of Aspergillus.ssp on wheat bran under Solid-State Fermentation carried out. Comparisons were made for phytase production. A. awamori NRC- F18 as the best phytase producer-strain cultured on different types of treated wastes followed by optimizing the fermentation conditions for enhancing phytase production using rice straw as the best substrate, which provides the highest phytase production. Thermostability of crude enzyme was studied. Statistical analyses were performed using SPSS at P < 0.05 or P < 0.01.

Results:

Bioinformatic studies predicted the most producer species and explained the difference in activity of phytases produced from different species, although they have the same function. All phytases of the selected fungal species from the database NCBI have highly conserved amino acid sequences; there are 88 identical positions; 135 similar positions, but the identity percentage was 16.858%. Experimental studies using five fungal strains of Aspergillus ssp. on wheat bran revealed optimum conditions for phytase production by A. awamori NRC- F18, which cultured on different types of treated wastes. A considerably higher phytase production was obtained using rice straw as substrate 424.66± 2.92 IU /g at pH 6 (371.883± 0.822 IU /g), after 144 hrs of incubation at 30°C. The maximum enzyme activity observed when solid: moisture was 1:4; Inoculum concentration 2mg/5g (418.363± 16.709 IU /g) and substrate concentration 4.5% (277.39± 12.05 IU /g). Glucose and Ammonium acetate were the best carbon and nitrogen sources that enhanced phytase production from A. awamori NRC- F18. The obtained phytase was found to be thermostable and the maximum temperature at which phytase still active was 80°C.

Conclusion:

Bioinformatic studies predicted the most producer species. Experimental study revealed that A.awamori NRC- F18 was the best Phytase -producer strain. Solid state fermentation was a good method; pretreatment of agriculture residues as rice straw was useful for less expensive phytase production, which was thermostable. A. awamori NRC- F18 can be used in the industrial production of phytase.

Screening of Fungal Strains for Cellulolytic and Xylanolytic Activities Production and Evaluation of Brewers’ Spent Grain as Substrate for Enzyme Production by Selected Fungi

Brewer’s spent grain (BSG), the solid residue of beer production, is attracting significant attention as raw material for the production of added value substances, since until recently it was mainly used as animal feed or deposited in landfills, causing serious environmental problems. Therefore, this work aimed at developing a bioprocess using BSG as a substrate for the production of cellulases and xylanases for waste saccharification and bioenergy production. Different fungi were analyzed for their cellulolytic and xylanolytic abilities, through a first screening on solid media by assessment of fungal growth and enzyme production on agar containing carboxylmethylcellulose or xylan as the sole carbon source, respectively. The best cellulase and xylanase producers were subjected to quantitative evaluation of enzyme production in liquid cultures. Aspergillus niger LPB-334 was selected for its ability to produce cellulase and xylanase at high levels and it was cultivated on BSG by solid state fermentation. The cellulase production reached a maximum of 118.04 ± 8.4 U/g of dry substrate after 10 days of fermentation, while a maximum xylanase production of 1315.15 ± 37.5 U/g of dry substrate was reached after 4 days. Preliminary characterization of cellulase and xylanase activities and identification of the enzymes responsible were carried out.

Production and characterization of a novel, thermotolerant fungal phytase from agro-industrial byproducts for cattle feed

OBJECTIVE

The application of phytases helps in releasing bound phosphorus and other nutrients in cattle feed eventually reducing the need for supplementations. However, high production cost owing to the unavailability of cheaper sources of phytases has limited their usage in developing countries. Herein, firstly isolation, identification of a phytase from fungal isolate, Aspergillus niger NT7 was carried out followed by optimizing of all production parameters, through solid-state fermentation (SSF). Secondly, crude phytase was characterized and potential applicability of crude phytase was evaluated for dephytinization of wheat bran.

RESULTS

The highest phytase production (208.30 ± 0.22 U/gds) was achieved using wheat bran as cheap agro-industrial substrate for SSF. The various physiological parameters were optimized including inoculum age and level (3-day old inoculum and 15 × 10⁷ spores/ml), temperature (35 °C), a moistening agent (distilled water), medium pH (5), and supplementation of various biochemicals like sugar (Mannitol), nitrogen (ammonium sulphate) and detergent (Tween 80). Process optimization through one variable at a time (OVAT) approach increased the difference in productivity to more than 200%. The crude phytase of A. niger NT7 was thermostable, with optimal activity at 60 °C and also displayed optimal activity over a broad range of acidic pH. Further, enhancement in phytase activity was found specifically in the presence of Ca²⁺, Zn²⁺, and Co²⁺ ions, while other metal ions including Fe²⁺, Fe³⁺, Mn²⁺, Mg²⁺and Cu²⁺ inhibited its activity. Finally, the phytase showed efficient and sustained release of inorganic phosphate, proteins, and reducing sugars (> 60 h) from livestock feed.

CONCLUSION

Overall, our report highlights the production of an efficient and thermotolerant phytase with potential as a low-cost animal feed supplement.

Dephytinizing and Probiotic Potentials of Saccharomyces cerevisiae (NCIM 3662) Strain for Amelioration of Nutritional Quality of Functional Foods

Increase of undigested complexes of phytic acid in food is gaining serious attention to overcome nutritional challenges due to chelation effects. We investigated soil-borne yeast phytase from Saccharomyces cerevisiae (NCIM 3662) for dephytinization of foods, probiotic properties, and process development. The strain produced 45 IU/DCG by cell-bound phytase in an unoptimized medium was increased fourfold (164 IU/DCG) in 12 h using statistical media optimization. The process was scaled-up up to 10-L fermenter scale with increased phytase productivity of 6.4 IU/DCG/h as compared to the lab scale. The strain displayed probiotic characteristics like tolerance to artificial gastric acid conditions, hydrophobicity, autoaggregation, coaggregation, and bile salt hydrolase (BSH) activity. Further, it could dephytinize (removal of phytic acid; an anti-nutritional factor) functional foods like ragi (finger millet) flour, soya flour, chickpea flour, and poultry animal feed. A combination of cell-bound dephytinizing phytase and nutrition-ameliorating probiotic traits of S. cerevisiae (NCIM 3662) presents profound applications in food technology sector.

Probiotic properties of a phytase producing Pediococcus acidilactici strain SMVDUDB2 isolated from traditional fermented cheese product, Kalarei

The nutritional challenge faced by the monogastric animals due to the chelation effects of phytic acid, fuel the research on bioprospecting of probiotics for phytase production. Pediococcus acidilactici SMVDUDB2 isolated from Kalarei, exhibited extracellular phytase activity of 5.583 U/mL after statistical optimization of fermentation conditions viz. peptone (1.27%); temperature (37 °C); pH (6.26) and maltose (1.43%). The phytase enzyme possessed optimum pH and temperature of 5.5 and 37 °C, respectively and was thermostable at 60 °C. The enzyme was purified 6.42 fold with a specific activity of 245.12 U/mg with hydrophobic interaction chromatography. The purified enzyme had K_m and V_max values of 0.385 mM and 4.965 μmol/min respectively, with sodium phytate as substrate. The strain depicted more than 80% survival rate at low pH (pH 2.0, 3.0), high bile salt concentration (0.3 and 0.5%), after gastrointestinal transit, highest hydrophobicity affinity with ethyl acetate (33.33 ± 0%), autoaggregation (77.68 ± 0.68%) as well as coaggregation (73.57 ± 0.47%) with Staphylococcus aureus (MTCC 3160). The strain exhibited antimicrobial activity against Bacillus subtilis (MTCC 121), Mycobacterium smegmatis (MTCC 994), Staphylococcus aureus (MTCC 3160), Proteus vulgaris (MTCC 426), Escherichia coli (MTCC 1652) and Lactobacillus rhamnosus (MTCC 1408). The amount of exopolysaccharide produced by the strain was 2 g/L. This strain having the capability of phytate degradation and possessing probiotic traits could find application in food and feed sectors.

Characteristics of an Acidic Phytase from Aspergillus aculeatus APF1 for Dephytinization of Biofortified Wheat Genotypes

Phytases are the special class of enzymes which have excellent application potential for enhancing the quality of food by decreasing its inherent anti-nutrient components. In current study, a protease-resistant, acidic phytase from Aspergillus aculeatus APF1 was partially purified by ammonium sulfate fractionation followed by chromatography techniques. The molecular weight of partially purified phytase was in range of 25-35 kDa. The purified APF1 phytase was biochemically characterized and found catalytically active at pH 3.0 and 50 °C. The K_m and V_max values of APF1 phytase for calcium phytate were 3.21 mM and 3.78 U/mg protein, respectively. Variable activity was observed with metal ions and among inhibitors, chaotropic agents and organic solvents; phenyl glyoxal, potassium iodide, and butanol inhibited enzyme activity, respectively, while the enzyme activity was not majorly influenced by EDTA, urea, ethanol, and hexane. APF1 phytase treatment was found effective in dephytinization of flour biofortified wheat genotypes. Maximum decrease in phytic acid content was noticed in genotype MB-16-1-4 (89.98%) followed by PRH₃-30-3 (82.32%) and PRH₃-43-1 (81.47%). Overall, the study revealed that phytase from Aspergillus aculeatus APF1 could be effectively used in food and feed processing industry for enhancing nutritional value of food.

Characterization of the Catalytic Structure of Plant Phytase, Protein Tyrosine Phosphatase-Like Phytase, and Histidine Acid Phytases and Their Biotechnological Applications

Phytase plays a prominent role in monogastric animal nutrition due to its ability to improve phytic acid digestion in the gastrointestinal tract, releasing phosphorus and other micronutrients that are important for animal development. Moreover, phytase decreases the amounts of phytic acid and phosphate excreted in feces. Bioinformatics approaches can contribute to the understanding of the catalytic structure of phytase. Analysis of the catalytic structure can reveal enzymatic stability and the polarization and hydrophobicity of amino acids. One important aspect of this type of analysis is the estimation of the number of β-sheets and α-helices in the enzymatic structure. Fermentative processes or genetic engineering methods are employed for phytase production in transgenic plants or microorganisms. To this end, phytase genes are inserted in transgenic crops to improve the bioavailability of phosphorus. This promising technology aims to improve agricultural efficiency and productivity. Thus, the aim of this review is to present the characterization of the catalytic structure of plant and microbial phytases, phytase genes used in transgenic plants and microorganisms, and their biotechnological applications in animal nutrition, which do not impact negatively on environmental degradation.

Purification and biochemical characterization of an Aspergillus niger phytase produced by solid-state fermentation using triticale residues as substrate

In this study, an extracellular phytase produced by Aspergillus niger 7A-1, was biochemically characterized for possible industrial application. The enzyme was purified from a crude extract obtained by solid-state fermentation (SSF) of triticale waste. The extract was obtained by microfiltration, ultrafiltration (300, 100 and 30 kDa) and DEAE-Sepharose column chromatography. The molecular weight of the purified enzyme was estimated to be 89 kDa by SDS-PAGE. The purified enzyme was most active at pH 5.3 and 56 °C, and retained 50% activity over a wide pH range of 4 to 7. The enzymatic thermostability assay showed that the enzyme retained more than 70% activity at 80 °C for 60 s, 40% activity for 120 s and 9% after 300 s. The phytase showed broad substrate specificity, a K_m value of 220 μM and V_max of 25 μM/min. The purified phytase retained 50% of its activity with phosphorylated compounds such as phenyl phosphate, 1-Naphthyl phosphate, 2-Naphthyl phosphate, p-Nitrophenyl phosphate and Glycerol-2-phosphate. The inhibition of phytase activity by metal ions was observed to be drastically inhibited (50%) by Ca⁺⁺ and was slightly inhibited (10%) by Ni⁺⁺, K⁺, and Na⁺, at 10 and 20 mM concentrations. A positive effect was obtained with Mg⁺⁺, Mn⁺⁺, Cu⁺⁺, Cd⁺⁺ and Ba⁺⁺ at 25 and 35% with stimulatory effect on the phytase activity.

Phytase production by solid-state fermentation of groundnut oil cake by Aspergillus niger: A bioprocess optimization study for animal feedstock applications

This investigation deals with the use of agro-industrial waste, namely groundnut oil cake (GOC), for phytase production by the fungi Aspergillus niger NCIM 563. Plackett-Burman design (PBD) was used to evaluate the effect of 11 process variables and studies here showed that phytase production was significantly influenced by glucose, dextrin, distilled water, and MgSO4 · 7H2O. The use of response surface methodology (RSM) by Box-Behnken design (BBD) of experiments further enhanced the production by a remarkable 36.67-fold from the original finding of 15 IU/gds (grams of dry substrate) to 550 IU/gds. This is the highest solid-state fermentation (SSF) phytase production reported when compared to other microorganisms and in fact betters the best known by a factor of 2. Experiments carried out using dried fermented koji for phosphorus and mineral release and also thermal stability have shown the phytase to be as efficient as the liquid enzyme extract. Also, the enzyme, while exhibiting optimal activity under acidic conditions, was found to have significant activity in a broad range of pH values (1.5-6.5). The studies suggest the suitability of the koji supplemented with phytase produced in an SSF process by the "generally regarded as safe" (GRAS) microorganism A. niger as a cost-effective value-added livestock feed when compared to that obtained by submerged fermentation (SmF).

Mixed Substrate Fermentation for Enhanced Phytase Production by Thermophilic Mould Sporotrichum thermophile and Its Application in Beneficiation of Poultry Feed

The optimum values of the critical variables determined by the central composite design of response surface methodology (RSM) for maximum phytase production (1881.26 U g(-1) dry mouldy residue (DMR)) by Sporotrichum thermophile are 2.5 % Tween 80, 1.0 % yeast extract and 48 h of incubation period. Phytase production in the mixed substrate (sugarcane bagasse and wheat bran) fermentation enhanced 11.6-fold over the initial production as a consequence of optimization. Phytase titres are sustainable in flasks, trays and column bioreactor (1796 to 2095 U g(-1) DMR), thus validating the model and the process for large-scale phytase production. When the yeast extract was replaced with corn steep liquor (2 % w/v), a sustained enzyme titre (1890 U g(-1) DMR) was attained, making the process cost-effective. Among all the detergents, Tween 80 supported a higher phytase production than others. The enzyme efficiently liberated nutritional components from poultry feed (inorganic phosphate, soluble protein and reducing sugars) in a time-dependent manner.

Isolation of a thermostable acid phytase from Aspergillus niger UFV-1 with strong proteolysis resistance

An Aspergillus niger UFV-1 phytase was characterized and made available for industrial application. The enzyme was purified via ultrafiltration followed by acid precipitation, ion exchange and gel filtration chromatography. This protein exhibited a molecular mass of 161 kDa in gel filtration and 81 kDa in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), indicating that it may be a dimer. It presented an optimum temperature of 60 °C and optimum pH of 2.0. The K M for sodium phytate hydrolysis was 30.9 mM, while the k cat and k cat / K M were 1.46 ×10 (5) s (-1) and 4.7 × 10 (6) s (-1) .M (-1) , respectively. The purified phytase exhibited broad specificity on a range of phosphorylated compounds, presenting activity on sodium phytate, p-NPP, 2- naphthylphosphate, 1- naphthylphosphate, ATP, phenyl-phosphate, glucose-6-phosphate, calcium phytate and other substrates. Enzymatic activity was slightly inhibited by Mg (2+) , Cd (2+) , K (+) and Ca (2+) , and it was drastically inhibited by F (-) . The enzyme displayed high thermostability, retaining more than 90% activity at 60 °C during 120 h and displayed a t 1/2 of 94.5 h and 6.2 h at 70 °C and 80 °C, respectively. The enzyme demonstrated strong resistance toward pepsin and trypsin, and it retained more than 90% residual activity for both enzymes after 1 h treatment. Additionally, the enzyme efficiently hydrolyzed phytate in livestock feed, liberating 15.3 μmol phosphate/mL after 2.5 h of treatment.

Optimization of solid-state fermentation for phytase production by Thermomyces lanuginosus using response surface methodology

A strain of Thermomyces lanuginosus, isolated from hot spring water in Turkey, was studied for optimization of phytase production using solid-state fermentation. Effects on fermentation of different production parameters such as substrate type, moisture, culture time, and inoculum size were investigated using a one-factor-at-a-time approach. Central composite design (CCD) of response surface methodology was applied for the optimization of four factors (culture temperature, initial pH, aeration area, age of seeding culture) that were affecting phytase production by Thermomyces lanuginosus in rice bran. Maximum phytase activity was achieved by using rice bran. The optimum levels of variables that supported maximum enzyme activity were moisture 70%, culture time 7 days, inoculum size 40%, culture temperature 55°C, initial pH 7.5, aeration area 30%, age of seeding culture 5 days, sucrose 1%, and ZnSO4 2.5 mM. An overall 10.83-fold enhancement in phytase activity (0.30 to 3.248 U) was attained due to the optimization.

Phytase production by Aspergillus oryzae in solid-state fermentation and its applicability in dephytinization of wheat bran [corrected]

Aspergillus oryzae SBS50 secreted a high titre of phytase in solid-state fermentation (SSF) using wheat bran at 30 °C after 96 h at the initial substrate to moisture ratio of 1:2 and a water activity of 0.95. The production of phytase increased when wheat bran was supplemented with sucrose and beef extract. Further enhancement in enzyme production was recorded when the substrate was supplemented with the surfactant Triton X-100 (145 U/g of DMB). An overall 29-fold improvement in phytase production was achieved owing to optimization. Under optimized conditions, the mould secreted 9.3-fold higher phytase in SSF as compared to submerged fermentation (SmF). The mesophilic mould also secreted amylase, cellulase (CMCase), pectinase and xylanase along with phytase in SSF. Scanning electron microscopy revealed luxuriant growth of A. oryzae on wheat bran with abundant spores. The enzyme dephytinized wheat bran with concomitant liberation of inorganic phosphate.

Current research and future perspectives of phytase bioprocessing

A focused platform for phytase bio-processing and application oriented research will help in developing an integrated technological solution to phytase production.

A bioprocess for the production of phytase from Schizophyllum commune: studies of its optimization, profile of fermentation parameters, characterization and stability

Schizophyllum commune produces phytase through solid-state fermentation using different agroindustrial residues. After optimization of phytase production, a maximal level of phytase (113.7 Units/gram of dry substrate) was obtained in wheat bran based medium containing 5% sucrose, 50% humidity, 7.5% of biomass at 33 °C pH 7.0 during 72 h and a 285% improvement in enzyme titre was achieved. Analysis of fermentation parameters profile for phytase production showed the highest productivity (1.466 Units/gram of dry substrate/hour) in 66 h of fermentation. Phytase has an optimal pH of 5.0, an optimal temperature of 50 °C and K (m) and V (max) values of 0.16 mM and 1.85 μmol mL(-1) min(-1), respectively. Phytase activity was stimulated essentially in the presence of K(+), Ca(2+), Mg(2+), Mn(2+), Zn(2+), Cu(2+), Fe(2+), Fe(3+), Co(2+), Ni(2+), acetate and citrate at concentrations of 1 mM. Phytase had the best shelf life when stored at a cooling temperature, maintaining 38% of its initial activity after 112 days of storage, and still presenting enzymatic activity after 125 days of storage. Stability studies of phytase performed in aqueous enzyme extracts showed satisfactory results using polyethyleneglycol 3350, carboxymethylcellulose, methylparaben, mannitol and benzoic acid in concentrations of 0.25, 0.025, 0.025, 0.25, and 0.0025%, respectively. PEG 3350 was shown to be the best stabilizing agent, resulting in 109% of phytase activity from the initial crude extract remaining activity in after 90 days.