Copra meal hydrolysis by the recombinant β-mannanase KMAN-3 and MAN 6.7 expressed in Escherichia coli
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Hydrolysis products of defatted copra meal (DCM) hydrolysis were investigated with either recombinant β-mannanases from Klebsiella oxytoca KUB-CW2-3 (KMAN-3) or Bacillus circulans NT 6.7 (MAN 6.7). Morphological changes and functional groups of solid residues were also determined by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Results revealed that the Michaelis–Menten constant (Km) and maximum velocity (Vmax) values of KMAN-3 on DCM were 2.4 mg/ml and 5.4 U/mg, respectively, while MAN 6.7 recorded Km and Vmax at 2.0 mg/ml and 4.3 U/mg, respectively. Both enzymes efficiently randomly hydrolysed DCM and produced a range of different manno-oligosaccharides (MOS). The profile of hydrolysis products was different for each enzyme used. Main products from hydrolysis of DCM by KMAN-3 and MAN 6.7 were various MOS including mannobiose (M2), mannotriose (M3), mannotetraose (M4), and mannose, whereas mannopentaose (M5) was only found from KMAN-3. Amount of M3 produced by KMAN-3 was about three times higher than from MAN 6.7. Total MOS yield for KMAN-3 was 1.5-folds higher than for MAN 6.7. SEM analysis showed that enzymatic hydrolysis with KMAN-3 and MAN 6.7 resulted in deconstruction of the DCM structure which generated a variety of MOS products. FTIR spectra revealed that the properties of both hydrolysed solids were not significantly different compared to the original DCM. Results suggested that KMAN-3 was a promising candidate for production of high MOS content from copra meal.
KeywordsManno-oligosaccharides Copra meal Recombinant β-mannanase Enzymatic hydrolysis
This research was supported by the Center for Advanced Studies for Agriculture and Food, Kasetsart University Institute for Advanced Studies, Kasetsart University under the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission, Ministry of Education, Thailand.
NP and SK conceived and designed experiments and wrote the manuscript. SU and SK gave some valuable advices about structure of manuscript. NP performed the experiments. All authors participated, read, and approved the final manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
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