Biological modification of pentosans in wheat B starch wastewater and preparation of a composite film.

ABSTRACT

BACKGROUND: Petrochemical resources are becoming increasingly scarce, and petroleum-based plastic materials adversely impact the environment. Thus, replacement of petroleum-based materials with new and effective renewable materials is urgently required. RESULTS: In this study, a wheat pentosan-degrading bacterium (MXT-1) was isolated from wheat-processing plant wastewater. The MXT-1 strain was identified using molecular biology techniques. The degradation characteristics of the bacteria in wheat pentosan were analyzed. The results show that wheat pentosan was effectively degraded by bacteria. The molecular weight of fermented wheat pentosan decreased from 1730 to 257 kDa. The pentosan before and after the biological modification was mixed with chitosan to prepare a composite film. After fermentation, the water-vapor permeability of the wheat pentosan film decreased from 0.2769 to 0.1286 g mm (m2 h KPa)-1. Results obtained from the Fourier-transformed infrared experiments demonstrate that the wave number of the hydroxyl-stretching vibration peak of the membrane material decreased, and the width of the peak widened. The diffraction peak of the film shifted to the higher 2θ, as seen using X-ray diffraction. The cross-section of the modified composite membrane was observed via scanning electron microscopy, which revealed that the structure was denser; however, no detectable phase separation was observed. These results may indicate improved molecular compatibility between wheat pentosan and chitosan and stronger hydrogen bonding between the molecules. Given the increased number of short-chain wheat pentosan molecules, although the tensile strength of the film decreased, its flexibility increased after fermentation modification. CONCLUSION: The findings of this study established that the physical properties of polysaccharide films can be improved using strain MXT-1 to ferment and modify wheat pentosan. The compatibility and synergy between pentosan and chitosan molecules was substantially enhanced, and hydrogen bonding was strengthened after biological modification. Therefore, modified pentosan film could be a potential candidate material for edible packaging films.