Linking Protein Quality in Biorefinery Output to Forage Crop Crude Protein Input via the Cornell Net Carbohydrate and Protein System

Abstract

The biorefinery technology aiming at protein extraction is rising and identification of suitable plant biomass input with valuable protein compounds for extraction is needed. Forage crops has been evaluated by the Cornell Net Carbohydrate and Protein System (CNCPS), and the result used as proxy of extractable protein in a biorefinery process. This serves as a helpful link between crop production and refinery output, however, the method has never been validated. Such validation is the main aim of this study. Five forage species: white clover, red clover, lucerne, perennial ryegrass and tall fescue were cut at four dates during spring and processed in a lab-scale refinery (screw press and subsequent green juice extraction). The pulp fraction and the precipitated protein concentrate were both CNCPS analyzed to follow the initial crude protein (CP) plant input into these two fractions.Total recovery in concentrate was highest for the legumes, which points to an advantage of these species in protein extraction setups. High recovery of B1 and B2 (50% or higher for the grasses) in the pulp demonstrated a large proportion of soluble protein ending up in the fibrous pulp and shed light on the reason behind high feed quality of the pulp fraction. In conclusion, the existing tentative assumption of extractable protein being equal to CNCPS fractions of B1 and B2 and partly B3 was shown to be too simplified. The presented findings can improve crop species screening in terms of expected extractable protein yield.

Annual protein yield and extractable protein potentials in three legumes and two grasses

“…piglets and chicken. The recovery percentages used are derived from Thers et al ., 19 which builds upon the extraction technique from Stødkilde et al ., 28 who, besides the single screw press treatment, also double screw pressed the plant matter in order to maximize the protein concentrate output. The double screw press procedure did indeed increase protein concentrate output; however, this was not evaluated by the Cornell method, and we therefore cannot say whether this changes the balances between forage species regarding specific CP fractions.…”

“…The recovery percentages reported in Thers et al 19 . were applied on the CNCPS analysis results from this study in order to estimate the potential refinery protein output in pulp and protein concentrate.…”

“…Among more methods for qualification of green biomass CP contents, the Cornell Net Carbohydrate and Protein System (CNCPS) represents one well‐defined and broadly used method 17,18 . By using this approach, a standardized evaluation of the CP forage crop content is obtained, which is linkable to potential refinery protein output via the recovery percentages in pulp and protein concentrate, which has been shown to deviate between forage species 19 . The CNCPS nomenclature divides the crude protein into different fractions, where A is non‐protein N, B is true protein and C is cell wall‐bound protein 20 .…”

“…The aim of this study was to evaluate yields and CP contents according to the CNCPS method for two full seasons (2 × 4 cuts) in three legumes and two grass species, the latter two fertilized at three nitrogen levels, resulting in nine field treatments in total. Further, the CP in the forage crop species were theoretically converted into potential biorefinery output CP yields and fractions of pulp and protein concentrate by using the recovery percentages previously reported by Thers et al 19 . We hypothesize (i) that the high‐N fertilized grasses will have the highest crude protein yield per hectare, (ii) that legumes will have higher crude protein concentrations compared to the grasses, and (iii) that legume species will show the highest level of potential extractable protein.…”

“…17,18 By using this approach, a standardized evaluation of the CP forage crop content is obtained, which is linkable to potential refinery protein output via the recovery percentages in pulp and protein concentrate, which has been shown to deviate between forage species. 19 The CNCPS nomenclature divides the crude protein into different fractions, where A is non-protein N, B is true protein and C is cell wall-bound protein. 20 Further, the B fraction is subdivided into B1, B2 and B3 based on decreasing solubility.…”