Elsevier

Biomass and Bioenergy

Volume 69, October 2014, Pages 47-57
Biomass and Bioenergy

Impact of ethanol bioprocessing on association of protein structures at a molecular level to protein nutrient utilization and availability of different co-products from cereal grains as energy feedstocks

https://doi.org/10.1016/j.biombioe.2014.06.014Get rights and content

Highlights

  • Corn and barley as energy feedstock were used for biofuel processing.

  • Co-products from biofuel processing differed in both protein nutritional profiles and protein structure.

  • Functional group amides have correlation with protein degradability, digestibility and total tract available protein.

  • Modeled protein structure α-helix to β-sheet ratio was correlated with protein digestion.

  • Biofuel processing impacts protein structure and nutrition interaction.

Abstract

The objective of this study was to study impact of ethanol (CAS # 64-17-5) processing on association of protein structures at a molecular level to protein nutrient utilization and availability of different co-products from cereal grains as energy feedstocks in China and to identify the correlation between protein molecular structures and protein nutritional profiles of co-products from ethanol bioprocessing in China in terms of: 1) protein chemical profiles; 2) protein subfractions; 3) total digestible protein; 4) protein degradation and estimated intestinal CP digestibility. The proteins molecular structure were determined using FT/IR-ATR molecular spectroscopy. The protein 2nd structure alpha-helix and beta-sheet were modeled based on amide I component peaks centered at ca. 1650 and 1630 cm−1, respectively identified by using 2nd derivative function. The protein subfractions were analyzed used CNCPS system. Total digestible protein were estimated according to a summary chemical approach in NRC model. Protein degradation and intestinal CP digestibility were determined using in situ nylon bag technique and three-step in vitro method, respectively. The results indicated that co-products from corn and barley differed in both protein nutritional profiles and protein structure parameters in terms of α-helix, β-sheet spectral intensity and their ratio and amide I, amide II spectral intensity and their ratio. Protein amide II height had a weakly positive correlation with (p < 0.05) PB2 fraction with R = 0.53, but that other protein amide parameters had no correlation with (p > 0.05) PA, PB1, PB3 and PC fractions. Protein amide II height had a positive correlation with (p < 0.05) TDN with R = 0.74. Protein amide II height has a negative correlation with (p < 0.05) protein degradability (R_DCP) with R = −0.67, and a positive correlation with (p < 0.05) intestinal protein digestibility (I_DCP) with R = 0.60, and a positive correlation with (p < 0.05) total tract available protein (T_ACP) with R = 0.58. For protein secondary structure, the α-helix to β-sheet ratio was negatively correlated with (p < 0.05) total protein digestibility (T_DCP) with R = −0.56 and positively correlated with (p < 0.05) total digestible crude protein (tdCP) with R = 0.55. In conclusion, the relationship between mid-IR spectroscopic data and nutritional profiles and digestibility parameters illustrated that the co-products intrinsic structures are closely related to nutritive quality, nutrient utilization and digestive behavior.

Introduction

As to protein value, most of published studies in the literature often focus on protein composition, not protein molecular structure. Protein quality relies not only on total protein content but also on inherent structures, such as protein secondary structures matrix, protein and carbohydrate combined matrix on the molecular basis [1], [2], [3]. Protein secondary structures mainly composed of alpha-helix and beta-sheet as well as a small amount of beta-turn and random coil [4], [5]. The secondary structures impacted on protein quality, protein utilization and availability [6], [7].

The great deal of co-products such as dried distiller grains with solubles (DDGS) has been produced with the high use of cereal grains (corn, wheat and barley) as energy stocks for ethanol and beer producing. Due to starch removal, the remaining chemical components in the distillers grains products become concentrated approximately threefold compare to the parent grain [8], [9]. Since its high protein content, DDGS has become a protein sourced feedstuff and is widely used in animal feed and livestock production industry. A systematical study on dry matter, mineral and other nutrient profiles of these co-products has been conducted using conventional ‘wet’ chemical analysis. On the other hand, several studies have been reported the information with protein structures. Especially the unique studies on correlation between protein molecular structure spectra and protein chemical and nutrient profiles, protein utilization and availability have been conducted by our research team in recent years. However, the research report how the molecular structure changes were associated with nutrient availability in the rumen and intestinal and total nutrient supply is still limited. Therefore, study on the protein molecular structures of these co-products can help us to have a better understanding to protein nutritional value.

The objectives of this study were: (1) to determine the protein chemical profiles, protein degradation and intestinal digestion of the co-products from cereal grains; (2) to reveal the protein molecular structures (in terms of amide I and amide II intensity and their ratio; ɑ-helix and β-sheet intensity and their ratio); (3) to investigate the relationship between protein molecular structures and chemical profiles, protein subfractions partitioned by Cornell Net Carbohydrate and Protein System (CNCPS), protein degradation and digestion; (4) to determine the most important structural features for the co-products from cereal grains. In this study, the hypothesis is that the protein molecular structure was associated with protein utilization and availability. Different ethanol and beer-making co-products have different protein molecular structures and different protein degradation and digestion behaviors.

Section snippets

Different types and sources of co-products from cereal grain

In this study, five corn DDGS and two barley DDGS samples were collected from seven different manufactures in the north of China from 2012 to 2013. They were numbered as “1, 2, 3, 4, 5, 6, and 7” samples according to the order of sampling.

This work was performed on substrates of unknown provenance, for which the chain of custody is not known. The species and the cultivars cannot be specified and while the authors BELIEVE that this work exemplifies the difference between DDGS processing - there

Protein profiles and protein subfractions

The detailed protein profiles and subfractions of the co-products are presented in Table 1. The results showed that the parameters of associated with protein, such as CP, NDICP, ADICP and SCP, were significant difference (p < 0.05) among the DDGS samples from different plants and derived from different grains. The changes in protein profiles among DDGS samples may be occur during processing, such as amount of added solubles, partial protein degradation during fermentation and Maillard product

Conclusion

In summary, different types and sources of the co-products from ethanol processing based cereal grain as energy feedstock in this study showed difference in protein nutrient and utilization profiles and protein internal structural makeup. Although the CLA and PCA analyses revealed similarity in protein molecular spectra, some protein molecular spectral feature of the co-products have relationship with protein nutrient utilization and availability to some extent. The difference in protein

Acknowledgments

Our research programs are supported by the Thousand-Talent-People Award Project in Tianjin, the Ministry of Agriculture Strategic Feed Research Chair Program, and the Natural Sciences and Engineering Research Council of Canada (NSERC-Individual Discovery Grant, Canadian federal government). The authors also thank Z. Niu (Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada) for his support with laboratory analysis and H. Xin for her help in ATR-FT/IR spectral

References (37)

  • P. Yu

    Synchrotron IR microspectroscopy for protein structure analysis: potential and questions: a review

    Spectroscopy

    (2006)
  • K. Theodoridou et al.

    Application potential of ATR-FT/IR molecular spectroscopy in animal nutrition: revelation of protein molecular structures of canola meal and presscake, as affected by heat-processing methods, in relationship with their protein digestive behavior and utilization for dairy cattle

    J Agric Food Chem

    (2013)
  • M. Jackson et al.

    The use and misuse of FTIR spectroscopy in the determination of protein structure

    Crit Rev Biochem Mol Biol

    (1995)
  • N.S. Marinkovic et al.

    Synchrotron infrared microspectroscopy

  • P. Yu

    Protein secondary structures (α-helix and β-sheet) at a cellular level and protein fractions in relation to rumen degradation behaviours of protein: a new approach

    Br J Nutr

    (2005)
  • J.C. Weigel et al.

    Feed co-products of the dry corn milling process

    (2009)
  • W.G. Nuez Ortín

    Variation and availability of nutrients in co-products from bio-ethanol production fed to ruminants

    (2010)
  • AOAC

    Official methods of analysis

    (1990)
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