Polyhydroxybutyrate (PHB) is a sought‐after alternative biopolymer to synthetics with its high biodegradability and similar properties to available polymers. However, its high production cost narrows its market application. In this study, cheap, biocompatible, and widely available fillers such as cellulose (CL) and calcium carbonate (CC) were incorporated into PHB using a heat‐assisted solution casting method to reduce the manufacturing cost of the bioplastic while retaining its properties. Characterization tests found that both natural fillers have relatively low miscibility with PHB which may be accounted for by self‐ and co‐agglomeration of the fillers while having improved thermal stability. The Young's modulus of the bioplastic films increased with the introduction of CC, while the mechanical property slightly decreased upon the addition of CL attributing to the aggregation of fillers. Full biodegradation of all composites within 8 weeks was observed in the compost biodegradability tests; PHB 90 CC 10 biodegraded the slowest after the 50th day, while PHB 90 CL 10 fully disintegrated after the 30th day. Further improvements such as the incorporation of cheap, naturally derived crosslinkers or plasticizers can greatly improve the properties of the synthesized biocomposites.

Polyhydroxybutyrate (PHB) is a biopolymer of natural origin, one of the suitable alternatives for synthetic plastics. However, pure PHB has a high production cost, is relatively brittle, and has poor processability, hence its limited application. Combining PHB with biomass fillers and plasticizers can significantly improve the properties of the polymer, leading to its commercial usage. In this study, PHB was incorporated with starch (S) as a cheap biomass filler and lauric acid (LA) as a potential plasticizer. The PHB/S/LA composites were prepared using a modified solvent casting method with the incremental addition of LA. The PHB/S ratio was maintained at a ratio of 80/20 (w/w). Physicochemical characterization via EDS, XRD, and FTIR proved that the composite components have blended through nucleation and plasticization processes. The morphology of the PHB/S blends was found to be a heterogeneous matrix, with decreased inhomogeneity upon the addition of LA in the composite. Thermal characterization done by TGA and DSC showed that the thermal properties of PHB/S films improved with the addition of LA. Mechanical tests (UTM) proved that the elastic strain of the films also increased with the addition of LA, although the tensile strength decreased slightly compared to pure PHB/S. Overall, the results of this study provide baseline information on the improvement of PHB-based bioplastics.

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Abstract:In this study, the photo fermentative H 2 production of Rhodobacter sphaeroides KCTC 1434 was investigated using acetate, propionate and butyrate under argon and nitrogen headspace gases. The highest H 2 yield and Substrate Conversion Efficiency (SCE) were observed from butyrate (8.84 mol H 2 /mol butyrate consumed, 88.42% SCE) and propionate (6.10 mol H 2 /mol propionate consumed, 87.16% SCE) under Ar headspace. Utilization of acetate was associated with low H 2 evolution, high biomass yield and high final pH, which suggest that acetate uptake by the strain involves a biosynthetic pathway that competes with H 2 production. The use of N 2 in sparging resulted to a decreased H 2 productivity in propionate (0.49 mol H 2 /mol propionate consumed, 7.01% SCE) and butyrate (1.22 mol H 2 /mol butyrate consumed, 1.04% SCE) and was accompanied with high biomass yield and radical pH increase in all acids. High H 2 generation had shown to improve acid consumption rate. The use of the three acids in a mixed substrate resulted to a drastic pH rise and lower H 2 generation. This suggests that a more refined culture condition such as additional control of pH during fermentation must be kept to enhance the H 2 productivity. Overall, the study provided a background on the H 2 production using R. sphaeroides KCTC 1434 which might be a good co-culture candidate because of its high SCE on butyrate and propionate.

Magnetic citric acid-modified cellulose was successfully produced and tested for the removal of copper in aqueous solution. Initially, the cellulose material was reacted with citric acid solution. The modified cellulose was then attached to the Fe2O3nanoparticle producing an adsorptive magnetic material. Characterization using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy indicated successful binding and chemical modification of the cellulose. Its adsorption was also studied to evaluate its potential in removing heavy metals such as copper. Removal of copper was as high as 84.74% in solution containing 25 mg/L copper. The sorption of copper in the magnetic sorbent follows second-order kinetics and best fits Freundlich isotherm model. The developed material has a strong magnetic response, thus its recovery in the aqueous solution could be easily facilitated using a magnetic field. Regeneration study indicated high recovery efficiency maintaining above 95.7% copper removal efficiency after three cycles of use. Thus, a highly efficient magnetic adsorptive material was produced using simple chemical modification aside from its easy recovery in the water.