Upgrading the Nutritional Value of PKC Using a Bacillus subtilis Derived Monocomponent β-Mannanase.

Helle Jakobe Martens,Janni Ulnits Nielsen,Luis-Miguel Gomez-Osorio,Reinhard Wimmer

doi:10.3390/molecules27020563

Helle Jakobe Martens, Janni Ulnits Nielsen + Show 2 more

Open Access

https://doi.org/10.3390/molecules27020563

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Abstract

Palm kernel cake (PKC) is an abundant side stream that can only be added to non-ruminant feed in small concentrations due to its content of antinutritional factors, mainly galactomannan, which cannot be digested by non-ruminants. β-mannanases can be added to partially hydrolyze galactomannan to form mannose oligosaccharides, which are known to be prebiotic. We here investigate the action of a β-mannanase from B. subtilis on PKC by colorimetry, NMR and fluorescence microscopy. The amount of mannan oligosaccharides in solution was significantly increased by the β-mannanase and their degree of polymerization (DP) was significantly reduced. There was a dose-response behavior in that larger β-mannanase concentrations increased the amount of soluble mannose oligosaccharides while reducing their average DP. Using confocal immunofluorescence microscopy, solubilization of galactomannan in PKC was clearly visualized. Images show a clear disruption of the cellulose and galactomannan structures of the PKC cell walls. We thus show in this study that using commercial dosages of β-mannanase on PKC can lead to formation of prebiotic compounds. Thus, this study suggests that utilization of PKC in poultry feed formulation might be increased by addition of a β-mannanase and would improve the return on investment.

Highlights

The past decades have seen a rising interest in supplementing animal feed formulations with byproducts from plant food production
With the export prices of palm oil from Asia soaring from an average of 660 USD/ton in February 2020 to 970 USD/ton, there is an increase in palm oil production and a concomitant increase in of the amount of resulting palm kernel cake (PKC) and, the potential gain of converting PKC to a high-value product increases [3]
At present, PKC can only be used in small amounts as a substitute for soybean meal (SBM) in poultry nutrition due to the high fiber content which acts as an antinutritional factor (ANF)

Summary

Introduction

The past decades have seen a rising interest in supplementing animal feed formulations with byproducts from plant food production This is in part due to a constant strain on the grain market in terms of high price volatility and availability and in part due to the growing concern for minimizing the carbon footprint of agriculture, where locally sourced byproducts are at an advantage over imported products [1]. One such byproduct is palm kernel cake (PKC) which remains after palm oil extraction by the expeller method. It is only chemical and biological treatments of PKC that seem to improve its nutrient value [4]

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