Retrofit Process Development for Phytate Extraction from Corn-Ethanol Coproducts Using Industrial Anion-Exchange Resins

Volumetric Scale-Up of a Packed-Bed Ion-Exchange System to Extract Phytate from Thin Stillage

Phytate is the main form of phosphorus in corn ethanol coproducts and poses digestion issues in monogastric-animal feed. Extracting phytate as a commodity chemical will bring extra revenue to the corn ethanol industry and reduces potential phosphorus pollution from livestock waste management. We assessed a simplified scale-up approach of an ion-exchange separation system applied to extract phytate from thin stillage using volumetric parameters and simplifications of the van Deemter model. Thin stillage is one of the main byproducts generated on dry-grind corn-to-ethanol plants and accounts for the liquid portion of the bottom product generated in the ethanol distillation process. Thin stillage is rich in dissolved phytate, which served as the basis for an ion-exchange extraction system developed with a scalability factor of 50. Under the evaluated conditions, similar breakthrough profiles were obtained when similar Péclet and Stanton numbers were maintained for the scales studied, demonstrating that a simple and straightforward scale-up can be attained if special attention is given to maintaining both parameters as the basis of calculations of the plate numbers of ion-exchange columns.

Phytase blends for enhanced phosphorous mobilization of deoiled seeds

Phytases are hydrolytic enzymes capable of a stepwise phosphate release from phytate which is the main phosphorous storage in seeds, cereals and legumes. Limitations such as low enzyme activity or incomplete phytate hydrolysis to inositol are a great challenge in phytase applications in food and feed. Herein we report a phytase blend of two enzymes with additive effects on phytate (InsP6) hydrolysis and its application in the enzymatic phosphorous recovery process. Blending the fast 6-phytase rPhyXT52 with the 3-phytase from Debaryomyces castellii, which is capable of fully hydrolyzing InsP6, we achieved rapid phosphate release with higher yields compared to the individual enzymes and a rapid disappearance of InsP6-3 intermediates, monitored by HPLC. NMR data suggest a nearly complete phytate hydrolysis to inositol and phosphate. The blend was applied for phosphate mobilization from phytate-rich biomass, such as deoiled seeds. For this emerging application, an up to 43% increased phosphate mobilization yield was achieved when using 1000 U of the blend per kg biomass compared to using only the E. coli phytase. Even so, the time of enzyme treatment was decreased by more than half (6 h instead of 16 h) when using 4000 U of blend, we reached a 78-90% reduction of the total phosphorous content in the explored deoiled seeds. In summary, the phytase blend of Dc phyt/rPhyXT52 was proven very efficient to obtain inositol phosphate depleted meal which has its potential application in animal feeding and is concomitant with the production of green phosphate from renewable resources.

Phosphorus fractionation and protein content control chemical phosphorus removal from corn biorefinery streams

The economic viability of corn biorefineries depends heavily on the sale of coproducts as animal feeds, but elevated phosphorus (P) contents can exacerbate manure management issues. Phosphorus removal from light steep water and thin stillage, two concentrated in-process aqueous streams at wet milling and dry-grind corn biorefineries, could simultaneously generate concentrated fertilizer and low-P animal feeds, but little is known regarding how differences in stream composition affect removal. To address this data gap, we show that the solubility of P in light steep filtrate (LSF) and thin stillage filtrate (TSF) exhibits distinct sensitivity to calcium (Ca) and base addition due to differences in P fractionation and protein abundance. In LSF, P was primarily organic, and near-complete removal of P (96%) was observed at pH 8 and a Ca/total P (TP) ratio of 2. In TSF, TP removal was lower (81%), and there was more equal distribution of organic and orthophosphate, indicating that the Ca requirements of inorganic P precipitation were a limiting factor. The C/H/N ratio, elemental characterization, and crude protein analysis of the precipitated solids indicated that coprecipitation of amorphous solids containing Ca, Mg, and K with soluble proteins facilitated removal of P, particularly in LSF. Although the removal mechanisms and solubility limits differed, these results highlighted the magnitude (40-70 mM) and efficacy (80-96%) of P recovery from two biorefinery streams.