Pretreatments to enhance the digestibility of lignocellulosic biomass

Lignocellulosic biomass represents a rather unused source for biogas and ethanol production. Many factors, like lignin content, crystallinity of cellulose, and particle size, limit the digestibility of the hemicellulose and cellulose present in the lignocellulosic biomass. Pretreatments have as a goal to improve the digestibility of the lignocellulosic biomass. Each pretreatment has its own effect(s) on the cellulose, hemicellulose and lignin; the three main components of lignocellulosic biomass. This paper reviews the different effect(s) of several pretreatments on the three main parts of the lignocellulosic biomass to improve its digestibility. Steam pretreatment, lime pretreatment, liquid hot water pretreatments and ammonia based pretreatments are concluded to be pretreatments with high potentials. The main effects are dissolving hemicellulose and alteration of lignin structure, providing an improved accessibility of the cellulose for hydrolytic enzymes. [1]


A MULTIENZYME TECHNIQUE FOR ESTIMATING PROTEIN DIGESTIBILITY

An in vitro method using a multienzyme system for the estimation of protein digestibility has been developed. The multienzyme system consists of trypsin, chymotrypsin and peptidase. It was found that the pH of a protein suspension immediately after 10 min digestion with the multienzyme solution was highly correlated with the in vivo apparent digestibility of rats. Regression analyses of 23 samples tested showed that the correlation coefficient between pH at 10 min and in vivo apparent digestibility was 0.90 with a standard error of estimate of 2.23. The regression equation was Y = 210.464 – 18.103, where “X” was the pH of protein suspension immediately after the 10 min digestion with the multienzyme solution. The most significant advantage of this in vitro method for predicting apparent protein digestibility was that it can be completed within 1 hr and with a high degree sensitivity. The method can detect the effects of trypsin inhibitor, chlorogenic acid, and heat treatment on protein digestibility. Strong buffer salts may affect the measurement of protein digestibility, but the buffering effects found in general food proteins and products tested did not create any problem with the procedure. [2]


Factors affecting sorghum protein digestibility

In the semi-arid tropics worldwide, sorghum (Sorghum bicolor (L.) Moench) is cultivated by farmers on a subsistence level and consumed as food by humans. A nutritional limitation to its use is the poor digestibility of sorghum protein when wet cooked. The factors affecting wet cooked sorghum protein digestibility may be categorised into two main groups: exogenous factors (grain organisational structure, polyphenols, phytic acid, starch and non-starch polysaccharides) and endogenous factors (disulphide and non-disulphide crosslinking, kafirin hydrophobicity and changes in protein secondary structure). All these factors have been shown to influence sorghum protein digestibility. More than one factor may be at play at any time depending on the nature or the state in which the sorghum grain is; that is whether whole grain, endosperm, protein body preparation, high-tannin or condensed-tannin-free. It is proposed that protein crosslinking may be the greatest factor that influences sorghum protein digestibility. This may be between γ- and β-kafirin proteins at the protein body periphery, which may impede digestion of the centrally located major storage protein, α-kafirin, or between γ- or β-kafirin and α-kafirin. [3]


Nutrient Digestibility and Growth Performance of Finisher Broilers Given Dried Xylopia aethiopica Fruits (Grains of Selim) as Additive

The nutrient digestibility and growth performance of finisher broilers given dried Xylopia aethiopica fruits (grains of selim) as additive was investigated. One hundred and ninety five finisher broilers (Arbor acres strain), 28- days old were randomly assigned into five treatments with each treatment having three replicates. Blended grains of selim was administered orally through drinking water on treatments 2, 3, 4 and 5 at concentrations of 0.4, 0.6, 0.8 and 1.0 g per litre respectively while birds on treatment 1 (control) received 0.3 g/litre of antibiotics (doxygen). Birds were fed ad libitum with the same isoproteinous and isocaloric diet containing 20% crude protein and 2905.95 Kcal/kg metabolisable energy for 28 days. Results showed no significant differences among treatments in the final body weight, total weight gain, daily weight gain, total feed intake, daily feed intake and feed conversion ratio. Nutrient digestibilities were similar across treatment groups. Results of this study demonstrated that grains of selim could be used as a substitute for antibiotic growth promoters. [4]

In vitro Starch Digestibility and Nutritional Composition of Improved Rice Varieties from Cameroun

Aims: Resistant starch (RS), kinetics of starch digestion, predicted glycemic index (pGI) and nutritional composition were determined in two improved rice varieties from Cameroun.

Place and Duration of Study: Department of Bioresource Engineering, McGill University, Canada between December 2012 and March 2013.

Methodology: Non-parboiled and parboiled samples of TOX 3145 and NERICA-3 varieties were involved in this study. An in vitro enzymatic starch digestion method was applied to measure starch digestibility parameters. Standardized methods were adopted for proximate and mineral contents evaluation.

Results: The parboiled samples had significantly higher (P<0.05) resistant starch (8.35 – 11.07%) than the non-parboiled samples (3.81 – 4.84%). The values for pGI among samples ranged from 57.57 to 67.78%. Significantly higher values for protein, phosphorus and potassium were found among the parboiled samples (P<0.05). Nutritional composition was positively related to RS while pGI had inverse relationship with protein, ash, fat, phosphorus, potassium and RS.

Conclusion: Starch digestibility of these rice varieties was associated to their nutritional composition. [5]

Reference

[1] Hendriks, A.T.W.M. and Zeeman, G., 2009. Pretreatments to enhance the digestibility of lignocellulosic biomass. Bioresource technology, 100(1), pp.10-18.

[2] Hsu, H.W., Vavak, D.L., Satterlee, L. and Miller, G.A., 1977. A multienzyme technique for estimating protein digestibility. Journal of Food Science, 42(5), pp.1269-1273.

[3] Duodu, K.G., Taylor, J.R.N., Belton, P.S. and Hamaker, B.R., 2003. Factors affecting sorghum protein digestibility. Journal of cereal science, 38(2), pp.117-131.

[4] Isikwenu, J.O., 2015. Nutrient digestibility and growth performance of finisher broilers given dried Xylopia aethiopica fruits (Grains of Selim) as additive. Journal of Experimental Agriculture International, pp.320-326.

[5] Odenigbo, A.M., Ndindeng, S.A., Nwankpa, C.A., Woin, N. and Ngadi, M., 2013. In vitro starch digestibility and nutritional composition of improved rice varieties from Cameroun. European Journal of Nutrition & Food Safety, pp.134-145.