Biodegradability testing methods being used nowadays have many disadvantages; they are time-consuming, inefficient medium used, and too much sample needed to do the test. This work aimed to study the biodegradability of starch-based bioplastics by modified ASTM G21-70 method using Salt Agar (SA) medium, dip-hanging method using sterile water, and Soil Burial Test (SBT) method. Bioplastics were prepared by mixing cassava starch and glycerol with a ratio of 3:1 (%, w/w) through a series of processes: (1) blending of starch and glycerol for 3 min, (2) extruding of the starch-glycerol mixture by using a single screw extruder at 80-130°C, and (3) compression molding at temperature and pressure of 150°C and 50 kgf/cm2, respectively. Aspergillus niger was used as bioplastic-degrading fungi for the modified ASTM G21-70 and dip-hanging methods, while compost-soil was used as a source of bioplastic-degrading microbes in SBT method. Bioplastics of 2x2 cm in size were applied to the tests for 10 days. The growth of fungi on the surface of bioplastics was observed visually at two days intervals. A. niger grew well on the surface of bioplastic sample in modified ASTM G21-70 method, indicated that the bioplastic could be degraded by the fungi. On the other hand, the growth of A. niger was poor in the dip-hanging method, even though weight loss of 11.5% occurred. Physical properties changing were indicated in the SBT method. On the 10th day, cracks were observed on the surface of the bioplastic sample, the color of the sample became darker even the bioplastic became fragile, and the weight loss reached 29.89%.

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The inulin fructotransferase (DFA III-forming)(EC 4.2.2.18) gene in Nonomuraea sp. ID06-A0189 was amplified from genomic DNA, sequenced and expressed in Escherichia coli. The 1326-bp gene, designated as Nsp-ift, encodes a protein composed of a putative 37-amino-acid signal peptide and 404-amino-acid mature protein. A putative ribosomal binding sequence was identified 12 bases upstream from the start codon. However, a typical bacterial promoter could not be found by in silico analysis. The deduced amino-acid sequence of the enzyme was most similar to that of inulin fructotransferase (DFA I-forming) in Frankia sp. EAN1pec. Phylogenetic analysis of deduced amino-acid sequences indicated that Nonomuraea sp. ID06-A0189 and Frankia sp. EAN1pec inulin fructotransferases formed a distinct clade from those from Arthrobacter sp. H65-7, A. globiformis and Bacillus sp. snu-7 that showed 57, 56 and 56% identity to that of Nsp-ift, respectively. The Nsp-ift without a putative signal peptide was successfully expressed in E. coli and partially purified using His-tag affinity chromatography. The recombinant enzyme displayed optimum temperature between 65 and 70 °C, optimum pH between 5.5 and 6.0 and remained stable up to 70 °C. The properties were identical to those of the original enzyme. Of 10 Nonomuraea species tested by Southern hybridization, enzyme activity measurements and PCR, only Nonomuraea sp. ID06-A0189 has the Nsp-ift gene, suggesting that Nsp-ift is not highly conserved in this genus.

Plastic wastes and petrochemical-based polymer materials have become a serious problem to the environment due to the characteristics of these materials that are difficult to degrade in nature. Polyhydroxyalkanoates (PHA) is one type of biodegradable plastics that have a great potential to replace the widely-used hydrocarbon plastics since it will decompose completely into carbon dioxide and water after burial for several months in the soil. PHA can be produced by microorganisms such as bacteria and algae through a fermentation process. The objective of this research is to obtain bacteria that can produce PHA. Screening was carried out by two sequential steps, qualitative and followed by quantitative methods. An amount of 29 bacteria strains isolated from Indonesians soil were screened for this purpose. The qualitative screening was conducted by growing the bacteria in a specific medium containing Nile red dye. The results showed that 19 strains were positive, generated pink to orange colonies under UV light at 235 nm. It was also confirmed by fluorescence microscope. The quantitative screening was performed by measuring the intracellular materials (predicted as PHA) of the bacterial cells by gravimetric method. The results indicated that the highest average of PHA content was 52.9%, 35.6% and 35.4 of dried cell weight, respectively for the Burkholderia sp B73, Bacillus sp B58, Bacillus toyonensis B50 and Staphylococcus cohni B66.

In this study, antioxidant activities and identification of the bioactive substances in L. (Gg) seed hard shell were evaluated. The seed of L., an Indonesian native plant, is commonly consumed as a vegetable or further processed as cracker. Isolated substances from seed are mainly stilbenoid derivatives which show potent antioxidant, tyrosinase inhibitor, and antimicrobial activities. Nevertheless, the antioxidant activity of its crude extract is still considered weak. In this study, an effort was made to improve antioxidant potency by fractionation using macroporous adsorptive resin (MAR). This fractionation successfully enhanced antioxidant activity of red Gg seed hard shell extract with efficient adsorption contact time within 30 min. Antioxidant activity of fractions 25-75% v/v ethanol increased three- to sevenfold as compared to crude extract and more importantly resulted in dry product which was easier for further processes. Identification of bioactive compounds in Gg seed hard shell extract with different degrees of ripeness was also performed by HPLC and confirmed the presence of Gnetin C, resveratrol, and other stilbenoid derivatives. These other stilbenoid derivatives could be the main substances contributing in antioxidant action with lower IC as compared to both Gnetin C and resveratrol. In summary, fractionation process using MAR HPD-600 reduced unnecessary sugar molecules from red Gg seed hard shell extract hence resulting to fraction with strong antioxidant activity.

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Anthocyanins extracted from purple-fleshed sweet potato were encapsulated using emulsification-crosslinking technique with chitosan acted as polymer and sodium tripolyphosphate as cross-linker. The parameters influencing microencapsulation were investigated i.e. stirring intensity and polymer concentration, pH of polymer and crosslinker solution, and also ratio of anthocyanins extract (core) to polymer concentration by characterizing the properties of obtained microcapsules. Stirring intensity of 1600 rpm achieved microcapsules with smaller mean diameter, narrower particle size distribution, and greater encapsulation efficiency than that of 1200 rpm for each similar polymer concentration. The research revealed that pH of 3.0 gave the greatest encapsulation efficiency and antioxidant activity of microcapsules. However, the different of mean diameter and particle size distribution of microcapsules for all of pH solution variation was not significant. Ratio of anthocyanins extract to polymer concentration 75% (w/w) possessed the greatest encapsulation efficiency, the biggest mean diameter and the widest particle size distribution between all of ratio variation. Meanwhile, ratio of 150% was selected for further analysis (microstructure and FT-IR) because it gave narrower particle size distribution and smaller mean diameter with its encapsulation efficiency was only little different from others ratio. Microstructure analysis by SEM revealed sphere and irregular microparticles. FT-IR analysis revealed that that there was bonding and interaction among anthocyanin, chitosan, and tripolyphosphate ion.