Scaffolds of cell substrates are biophysical platforms for cell attachment, proliferation, and differentiation. They ultimately play a leading-edge role in the regeneration of tissues. Recent studies have shown the potential of bioactive scaffolds (i.e., osteo-inductive) through 3D printing. In this study, rice bran-derived biocomposite was fabricated for fused deposition modeling (FDM)-based 3D printing as a potential bone-graft analogue. Rice bran by-product was blended with poly caprolactone (PCL), a synthetic commercial biodegradable polymer. An extruder with extrusion process molding was adopted to manufacture the newly blended “green material.” Processing conditions affected the performance of these blends. Bio-filament composite was characterized using field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX). Mechanical characterization of bio-filament composite was carried out to determine stress-strain and compressive strength. Biological behaviors of bio-filament composites were also investigated by assessing cell cytotoxicity and water contact angle. EDX results of bio-filament composites indicated the presence of organic compounds. These bio-filament composites were found to have higher tensile strength than conventional PCL filament. They exhibited positive response in cytotoxicity. Biological analysis revealed better compatibility of r-PCL with rice bran. Such rice bran blended bio-filament composite was found to have higher elongation and strength compared to control PCL.

본 연구에서는 1톤 용량의 배아미를 생산할 수 있는 중형 배아미 생산시스템의 설계, 개발 그리고 평가를 목표로 하였다. 개발된 배아정미기는 연삭과 마찰의 혼합방식으로 제조되었다. 배아미 생산시스템의 형태는 2대의 직렬 입형 배아정미기로 구성하였으며, 배아부착율, 백도, 싸래기율을 조사하였다. 또한, 연삭식, 마찰식, 연삭과 마찰의 혼합방식에 따라서 각각 배아미의 배아부착율, 백도, 싸래기율도 조사하였다. 본 시스템은 1단계 배아정미기에서는 연삭과 마찰의 혼합방식으로 미강을 깍은 후, 2번째 배아 정미기에서는 쌀의 배아가 떨어지지 않도록 미세 미강을 제거하면서 쌀의 백도를 높이도록 개발되었다. 배아정미기 시작기에서는 축 롤러 부분의 금강석 연삭돌을 3개, 스크린부에는 6개의 연삭돌을 설치하였고, 각각의 정미기 롤러축의 회전속도는 960 rpm과 780 rpm으로 하여 배아 부착율과 백도를 높였다. 그 결과, 약 20%의 배아 부착율을 증가시킬 수 있었다. 본 연구에서는 다음과 같이 요약할 수 있다. 첫째, 배아부착율은 현미의 함수율과 밀접한 관계가 있었다. 함수율 15.2±0.1%인 시료로 실험한 결과, 투입량 약 600 kg일 때 배아부착률은 약 70%를 나타내었다. 둘째, 배아미의 백도는 정미기 롤러축의 회전속도 960 rpm 과 780 rpm 조건으로 운전하였을 때 각각 35, 37 백도로 향상시킬 수 있었다. 셋째, 싸래기율은 본 시스템에서 1% 미만으로 나타냈다. 본 연구에서 개발된 연식마찰식 배아정미기를 평가해본 결과 배아부착율, 백도, 싸래기율을 효과적으로 개선할 수 있었고 30%의 에너지 이용을 절감할 수 있었다.

Chemical batch tests were conducted to investigate the amount of nutrients that were released from the wasted activated sludge during microwave heating. For this study, three types of activated sludge were obtained from A2/O, MLE and oxidation ditch (OD) processes. Polyphosphate-accumulating organisms in the activated sludge have a unique trait: they releases phosphate from the cell when they are exposed to high temperatures. The sludge obtained from the A2/O process released the largest amount of phosphate, followed by those from the MLE and OD processes. The release of phosphate increased with increasing polyphosphate content in the sludge under strongly alkaline or acidic conditions. Furthermore, ammonia and heavy metals were released with phosphorous. The largest amount of ammonia was observed from the sludge obtained from the MLE process. The release of heavy metals strongly depends on the pH conditions. Therefore, the chemical analysis results strongly suggest that both phosphorus and ammonia react with Mg2+ or Ca2+ to form metal complexes such as magnesium ammonium phosphate or hydroxyapatite under alkaline conditions.

This study was conducted to investigate the feasibility of nutrient recovery and reuse from centrate, which was produced by the centrifugal dewatering of anaerobic digested sludge. A continuous stirred reactor was operated for 3 months to recover phosphorous and nitrogen as magnesium ammonium phosphate (MAP) crystals from the centrate. More than 95% of phosphate could be recovered from the centrate into the crystalline materials. The contents of TP and TN in the crystalline materials were 28.1% and 5.17%, respectively. Some heavy metals were identified, but remained under Korean standards for organic fertilizer. On the other hand, X ray diffraction analysis clearly showed that the crystalline materials was MAP crystals. However, chemical analyses suggested that some undesirable crystals like magnesium potassium phosphate or hydroxyapatite might be formed during the MAP crystallization. Nevertheless, both results strongly confirmed that the MAP crystals could be a useful and valuable nutrient fertilizer, which slowly and continuously releases essential nutrients in response to the demand from farming and planting.