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The incorporation of fermented chitin nanowhiskers (FCHW) into poly(lactic acid) (PLA) increased the tensile modulus and strength of PLA at the expense of ductility. The brittleness of PLA can be overcome with the use of plasticizer such as polyethylene glycols (PEG). The objective of this study is to investigate the effect of FCHW on the tensile and thermal properties PLA incorporated with PEG as plasticizer (PLA/PEG). PLA/PEG and FCHW reinforced PLA/PEG nanocomposites were prepared using solution mixing technique. Thermogravimetric analysis (TGA) was used to determine the thermal properties while tensile properties were determined from the tensile test. The incorporation of PEG successfully increased the ductility and tensile strength of PLA at the expense of modulus. Based on the tensile properties, 5 phr PEG was chosen for further investigation on the effect of FCHW on PEG modified PLA. Incorporation of 1 phr FCHW PLA/PEG increased the tensile strength and Young’s modulus. However, the tensile strength decreased with further addition of FCHW. The elongation at break of PLA/PEG decreased drastically with the incorporation of 1 phr FCHW and decreased gradually with further increase of FCHW. The thermal stability from TGA of FCHW reinforced PLA/PEG nanocomposites at 5 phr FCHW content was observed to be significantly higher compared to PLA/PEG, as indicated by T20 and Tmax.

This study investigates the use of chitin nanowhiskers (CHW) from different chitin sources to develop CHW reinforced polylactic acid (PLA) nanocomposite. Chitin sources used in this study were commercial chitin (CC), fermented chitin (FC) and treated fermented chitin (TFC) whereby FC and TFC were obtained from fermentation of prawn waste. The chitin was then undergoes acid hydrolysis to produce commercial chitin nanowhiskers (CCHW), fermented chitin nanowhiskers (FCHW) and treated fermented chitin nanowhiskers (TFCHW). PLA was chosen due to several advantages such as biodegradability, good mechanical strength and in line with global pressure to improve environmental pollution aspects. Tensile strength for PLA/FCHW, PLA/TFCHW and PLA/CCHW increased with increasing filler content until it reached optimum value at 1 phr, 2 phr and 3 phr, respectively. Young’s modulus for the nanocomposites increased with increasing filler content but elongation at break decreased significantly with increasing filler content for all types of nanocomposites. TGA results indicated that PLA/CHW nanocomposites displayed better thermal stability as compared to pure PLA. The biodegradability and water absorption of nanocomposites increased with increasing filler content.The overall results confirm that PLA nanocomposites from FC are not inferior than PLA nanocomposites from CC and therefore has similar potential to be used in packaging applications. ABSTRAK: Kajian ini menyelidik penggunaan nanowisker kitin (CHW) dari sumber kitin yang berbeza untuk membangunkan komposit poli(asid laktik) (PLA) bertetulang CHW. Sumber-sumber kitin yang digunakan dalam kajian ini terdiri daripada kitin komersial (CC), kitin ditapai (FC) dan kitin ditapai yang dirawat (TFC) di mana FC dan TFC diperoleh daripada penapaian sisa udang. Kitin kemudiannya menjalani proses hidrolisis asid untuk menghasilkan nanowisker kitin komersial (CCHW), nanowisker kitin ditapai (FCHW) dan nanowisker kitin ditapai yang dirawat (TFCHW). PLA dipilih kerana kelebihannya misalnya kebolehan pereputan-bio, kekuatan mekanikal yang baik dan sesuai dengan tekanan global untuk memperbaiki aspek pencemaran alam sekitar. Kekuatanreganganuntuk PLA/FCHW, PLA/TFCHW dan PLA/CCHW meningkat dengan peningkatan kandungan pengisi sehingga mencapai nilai optimum masing-masing pada 1 phr, 2 phr dan 3 phr. Modulus Young bagi komposit nano meningkat dengan peningkatan kandungan pengisi tetapi ciri pemanjangan takat putus menurun dengan ketara dengan peningkatan kandungan pengisi bagi semua jenis komposit nano. Keputusan TGA menunjukkan bahawa komposit nano PLA/CHW memaparkan kestabilan terma yang lebih baik berbanding dengan PLA tulen. Kadar pereputan-bio dan penyerapan air komposit nano meningkat dengan peningkatan kandungan pengisi. Hasil keseluruhan mengesahkan bahawa komposit nano PLA daripada FC tidak lebih rendah daripada komposit nano PLA dari CC dan berpotensi serupa untuk digunakan dalam aplikasi pembungkusan.

The topic on bioplastics is of considerable interest with respect to environmental pollution caused by non-biodegradable plastics. Great efforts have been made in producing biomaterials with minimum negative impacts towards the environment. Bioplastics accounted 1% of the 335 million tonnes of plastic production in a year. The market and demand are continuously growing as the development of new biopolymers, applications and products are emerging. The objective of the review work reported in this chapter is to provide recent advances and challenges in the utilization of agricultural waste (agro-waste) or by-products in the production of bioplastics; namely polylactic acid, thermoplastics starch and chitosan bioplastic. Various agro waste that has potential to be used as bioplastics are bagasse, corn cob, cellulose, sago pith waste and chitin. The trend of agro-waste as the source for bioplastics production is rising due to the relatively lower cost and easily available. However, the utilization of agro-waste for development of bioplastics is still limited due to the unsystematic and low cost-effective waste management system, limited data on waste generation, and low production yield compared to food feedstock. It is believed that the prospect of agro-waste as feedstock for bioplastics will improve with the advancement in biotechnology and government intervention. Government, public, industrialists and researchers should synergize to realize the commercialization of agro waste-derived bioplastics.

To overcome drawbacks in the conventional chemical route to synthesize eugenyl benzoate, immobilized Rhizomucor miehei lipase (RML) as the biocatalyst was proposed. The RML conjugated to a hybrid support consisting of biopolymers, chitosan (CS) and chitin nanowhiskers (CNWs). 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDAC) was used as the crosslinker to bind the lipase. Immobilization of RML was the highest on crosslinked CS/CNWs which gave a protein loading of ∼8.12 mg/g, corresponding to specific and residual activity of 537 U/g and 137%, respectively. Fourier transform infrared spectroscopy, thermogravimetric analysis-differential thermogravimetry, field emission scanning electron and atomic force microscopy of RML-CS/CNWs revealed that RML was successfully attached to the surface of crosslinked CS/CNWs. Under an optimized condition, the highest yield of eugenyl benzoate (56.3%) was attained after 5 h using 3 mg/mL of RML-CS/CNWs with molar ratio of eugenol: benzoic acid of 3:1, as compared to only 47.3% for the free RML. Analyses of FTIR and NMR on purified eugenyl benzoate affirmed that the ester was successfully produced in the enzymatic esterification. Therefore, the use of the RML-CS/CNWs biocatalysts appears promising to afford good yields of eugenyl benzoate within a relatively shorter reaction time.

A biotechnological route via enzymatic esterification was proposed as an alternative way to synthesize the problematic anti-oxidant eugenyl benzoate. The new method overcomes the well-known drawbacks of the chemical route in favor of a more sustainable reaction process. The present work reports a Box-Behnken design (BBD) optimization process to synthesize eugenyl benzoate by esterification of eugenol and benzoic acid catalyzed by the chitosan-chitin nanowhiskers supported Rhizomucor miehei lipase (RML-CS/CNWs). Effects of four reaction parameters: reaction time, temperature, substrate molar ratio of eugenol: benzoic acid and enzyme loading were assessed. Under optimum conditions, a maximum conversion yield as high as 66% at 50°C in 5h using 3mg/mL of RML-CS/CNWs, and a substrate molar ratio (eugenol: benzoic acid) of 3:1. Kinetic assessments revealed the RML-CS/CNWs catalyzed the reaction via a ping-pong bi-bi mechanism with eugenol inhibition, characterized by a Vmax of 3.83mMmin-1. The Michaelis-Menten constants for benzoic acid (Km,A) and eugenol (Km,B) were 34.04 and 138.28mM, respectively. The inhibition constant for eugenol (Ki,B) was 438.6mM while the turnover number (kcat) for the RML-CS/CNWs-catalyzed esterification reaction was 40.39min-1. RML-CS/CNWs were reusable up to 8 esterification cycles and showed higher thermal stability than free RML.

The objective of this study is to investigate the effects of partial replacement of montmorillonite (MMT) with microcrystalline cellulose (MCC) on the biodegradability and thermal properties of hybrid MMT/MCC filled polylactic acid (PLA) composites prepared using solution casting technique. Based on our previous study, the optimum MMT content based on having the highest tensile strength in PLA/MMT nanocomposites is 5 phr (parts per hundred parts of polymer). Therefore, the PLA/MMT/MCC hybrid composites were prepared at a total filler content of 5 phr. The biodegradability and thermal properties of PLA hybrid composites were investigated using soil burial test and thermogravimetric analysis, respectively. The biodegradability of PLA/MMT/MCC hybrid composites (1 phr MMT and 4 phr MCC) at 8th week significantly increased by approximately 228% and 367% compared to the optimum formulation of PLA/MMT nanocomposite and neat PLA, respectively. In addition, Fourier transform infrared spectroscopy (FTIR) revealed the formation of hydrogen bonding between the fillers and PLA matrix. The thermal stability of hybrid composites improved from 358.3 to 362.2 °C by incorporation of hybrid MMT/MCC (1 phr MMT and 4 phr MCC) into PLA matrix, as demonstrated by maximum decomposition temperature.

Polylactic acid (PLA) nanocomposites reinforced with hybrid montmorillonite/cellulose nanowhiskers [MMT/CNW(SO4)] were prepared by solution casting. The CNW(SO4) nanofiller was first isolated from microcrystalline cellulose using acid hydrolysis treatment. PLA/MMT/CNW(SO4) hybrid nanocomposites were prepared by the addition of various amounts of CNW(SO4) [1-9 parts per hundred parts of polymer (phr)] into PLA/MMT nanocomposite at 5 phr MMT content, based on highest tensile strength values as reported previously. The biodegradability, thermal, tensile, morphological, water absorption and transparency properties of PLA/MMT/CNW(SO4) hybrid nanocomposites were investigated. The Biodegradability, thermal stability and crystallinity of hybrid nanocomposites increased compared to PLA/MMT nanocomposite and neat PLA. The highest tensile strength of hybrid nanocomposites was obtained by incorporating 1 phr CNW(SO4) [∼ 36 MPa]. Interestingly, the ductility of hybrid nanocomposites increased significantly by 87% at this formulation. The Young's modulus increased linearly with increasing CNW(SO4) content. This is due to the relatively good dispersion of nanofillers in the hybrid nanocomposites, as revealed by transmission electron microscopy. Fourier transform infrared spectroscopy indicated the formation of some polar interactions. In addition, water resistance of the hybrid nanocomposites improved and the visual transparency of neat PLA film did not affect by addition of CNW(SO4).

In this study, hybrid montmorillonite/cellulose nanowhiskers (MMT/CNW) reinforced polylactic acid (PLA) nanocomposites were produced through solution casting. The CNW filler was first isolated from microcrystalline cellulose by chemical swelling technique. The partial replacement of MMT with CNW in order to produce PLA/MMT/CNW hybrid nanocomposites was performed at 5 parts per hundred parts of polymer (phr) fillers content, based on highest tensile strength values as reported in our previous study. MMT were partially replaced with various amounts of CNW (1, 2, 3, 4 and 5phr). The tensile, thermal, morphological and biodegradability properties of PLA hybrid nanocomposites were investigated. The highest tensile strength of hybrid nanocomposites was obtained with the combination of 4phr MMT and 1phr CNW. Interestingly, the ductility of hybrid nanocomposites increased significantly by 79% at this formulation. The Young's modulus increased linearly with increasing CNW content. Thermogravimetric analysis illustrated that the partial replacement of MMT with CNW filler enhanced the thermal stability of the PLA. This is due to the relatively good dispersion of fillers in the hybrid nanocomposites samples as revealed by transmission electron microscopy. Interestingly, partial replacements of MMT with CNW improved the biodegradability of hybrid nanocomposites compared to PLA/MMT and neat PLA.

The objective of this study is to investigate the effect of partial replacement of montmorillonite (MMT) with microcrystalline cellulose (MCC) on the tensile and morphology properties of polylactic acid (PLA) composites. PLA composites reinforced with hybrid MMT/MCC were prepared by solution casting. Based on our previous study, tensile strength exhibited that the optimum MMT content in the PLA/MMT is 5 phr. Therefore, partial replacement of MMT with MCC was performed at 5 phr of filler content in order to produce PLA/MMT/MCC hybrid composites. Fourier transform infrared spectroscopy revealed some polar interaction between fillers and PLA matrix. Young’s modulus of the PLA/MMT/MCC hybrid composites increased gradually with increasing MCC filler in the hybrid composites and was higher than PLA/MMT nanocomposites. However, the highest tensile strength of hybrid composites was obtained at 4 phr MMT and 1 phr of MCC filler (~26 MPa), which was lower than optimum formulation of PLA/MMT nanocomposites. Interestingly, the percent elongation at break of the hybrid composites were higher than that of PLA/MMT nanocomposites; increased significantly from ~10 to ~58 %. Field emission scanning electron microscopy indicated the aggregation of MCC and the presence of some cracks in the PLA hybrid composites, resulted in decrease of the tensile strength.

The objective of this study is to investigate the effects of incorporating microcrystalline cellulose (MCC) on montmorillonite (MMT) reinforced polylactic acid (PLA) nanocomposites prepared by solution casting method. The biodegradability, tensile and morphological properties of PLA hybrid composites were investigated using soil burial test, tensile testing machine, field emission scanning electron microscopy, transmission electron microscopy (TEM) and optical microscopy. In addition, Fourier transform infrared spectroscopy (FTIR) was used to observe the interactions between fillers and PLA in the hybrid composites. Various amounts of MCC were added to the optimum formulation which was 5 phr of MMT to produce PLA/MMT/MCC hybrid composites. The biodegradability of hybrid composites increased compared to nanocomposite with 5 phr MMT content and neat PLA. Interestingly, the ductility of PLA/MMT/MCC hybrid composites increased significantly with the addition of 1 phr MCC filler. FTIR analysis revealed some interactions between PLA and both fillers in the hybrid composites. X-ray diffraction and TEM analyses revealed that incorporation of MCC filler into optimum formulation of PLA/MMT nanocomposites slightly decreased the interlayer spacing of MMT in the PLA/MMT/ MCC hybrid composites.

Montmorillonite (MMT)/cellulose nanowhiskers (CNW) reinforced polylactic acid (PLA) hybrid nanocomposites were prepared by solution casting. CNW were isolated from microcrystalline cellulose using a chemical swelling method. An initial study showed that the optimum MMT content, for mechanical properties, in a PLA/MMT nanocomposite is five parts per hundred parts of polymer (phr). Various amounts of CNW were added to the optimum formulation of PLA/MMT to produce PLA/MMT/CNW hybrid nanocomposites. FT-IR analysis indicated the formation of some polar interactions, resulting in enhanced tensile properties of the hybrid nanocomposites. The highest tensile strength for the hybrid nanocomposites was obtained for a 1 phr CNW content. Young’s modulus was also found to increase with an increasing CNW content. Interestingly, the strain to failure (or ductility) of the hybrid nanocomposites increased significantly from ~10 to ~90 % with the addition of 1 phr CNW. This increase in ductility was proposed to be due to the nucleation of crazes and the formation of shear bands in the PLA.

Over the past decade, there has been a growing interest in the use of natural fibers in biocomposites both in industrial applications and fundamental research due to its many advantages such as low cost, lightweight, and environmentally friendly. In addition, natural fibers have a higher specific strength compared with glass fibers and a similar specific modulus. The natural fiber biocomposites are more environmentally friendly, which are highly used in building and construction industries, transportation, packaging, and consumer products. Rice husk (RH) and kenaf fibers (KF) are the most common used natural fibers. RH and KF are well-known as a cellulosic source with economic and ecological advantages. As a type of natural fiber obtained from agro-industrial waste, RH and KF can be used as fillers in polypropylene (PP) biocomposites. This study is aimed at highlighting previous works on RH and KF reinforced PP biocomposites to provide information for applications and further research in this area. Based on the information gathered, application of RH and KF reinforced PP biocomposites as alternative materials in building and construction is highly plausible with both lightweight and low cost as its main driving forces.

In this chapter, the effects of two different preparation methods of cellulose nanowhiskers (CNW) on the tensile, thermal, morphological, and biodegradability properties of montmorillonite (MMT)-reinforced polylactic acid (PLA) were investigated. The CNWs were obtained from microcrystalline cellulose using chemical swelling (CNW-CS) and sulfuric acid hydrolysis (CNW-AH). Based on tensile properties, the optimum MMT content in PLA/MMT nanocomposites is five parts per hundred parts of polymer (phr) [P/MT5]. The PLA/MMT/CNW-CS and PLA/MMT/CNW-AH hybrid nanocomposites were produced using solution casting by the addition of various amounts of CNW-CS and CNW-AH fillers into P/MT5 nanocomposite, respectively. The highest tensile strength for the hybrid nanocomposites was obtained at 1 phr CNW-CS and CNW-AH content. Interestingly, the ductility of the hybrid nanocomposites increased significantly from ~10 to ~90 and ~87% with the addition of 1 phr CNW-CS and CNW-AH, respectively. The biodegradability and thermal stability of hybrid nanocomposites improved compared to P/MT5 nanocomposite and neat PLA.

The effects of formulation design on the tensile, morphological, and biodegradability properties of hybrid cellulose nanowhiskers/montmorillonite (CNW/MMT) reinforced polylactic acid (PLA) nanocomposites were investigated in this chapter. The CNWs were obtained from microcrystalline cellulose (MCC) using chemical swelling with N,N-dimethylacetamide containing 0.5% lithium chloride. Based on the tensile properties of PLA/MMT nanocomposites, 5 phr (parts per hundred parts of resin) MMT was selected as optimum content (P/MT5/CW0). The PLA/MMT/CNW hybrid nanocomposites were prepared using two different sets of formulations by solution casting method. The hybrid nanocomposites were produced by incorporation of different content of CNW (1, 3, 5, 7, and 9 phr) into P/MT5/CW0 nanocomposite and partial replacement of MMT with CNW at total filler content of 5 phr. The highest tensile strength for the PLA/MMT/CNW hybrid nanocomposites was obtained at 1 phr CNW for both sets of formulations. Interestingly, the ductility of the hybrid nanocomposites increased remarkably from approximately 10 to 90 and 79% by incorporation of 1 phr CNW into P/MT5/CW0 nanocomposite and partial replacement of 1 phr MMT with CNW, respectively. Furthermore, the biodegradability of PLA/MMT/CNW hybrid nanocomposites improved compared to neat PLA and optimum formulation of PLA/MMT nanocomposites.

In the past decade, a growing interest in the use of green nanocomposites in industrial applications has been observed because of many advantages such as biodegradability, renewability and their relatively low cost to substitute the conventional petroleum-based polymers. The nanocomposites based on polylactic acid (PLA) have the potential to be used in automotive applications due to good mechanical properties and processability. This chapter highlights the recent developments on PLA nanocomposites as potential materials for automotive applications. One of the common methods to improve the performances of PLA is the combination of PLA with various nanofillers including layered silicates and carbon derivatives such as graphene and carbon nanotubes. Mechanical and thermal properties are the focus of this chapter as the properties are important for automotive applications. Further research in this area is also being proposed.

The market share of biodegradable polymers from renewable sources has grown rapidly in the plastic industry. Properties of the polymers from renewable resources can be enhanced through blending and composite formation. Fermented chitin is a by-product in a bacterial prawn waste fermentation for protein recovery which has undergone mild chemical treatment producing treated fermented chitin (TFC). TFC was further acid hydrolysed to produce chitin nanowhiskers (TFCNW). The chitin nanowhiskers was used as filler in polylactic acid (PLA) through solution casting method. Atomic Force Microscopy showed TFCNW particles are uniformly dispersed in PLA matrix but tends to agglomerate as TFCNW loading increased. Tensile strength of the biocomposite film increased up to 12.4 MPa at 2 phr TFCNW which it decreased with further addition of TFCNW. The Young’s modulus increased with increasing of TFCNW content up to 3.69 GPa. However, elongation at break of the biocomposite film decreased by 66 % upon addition of TFCNW when compared to pure PLA.

The objective of this study is to compare the effect of two different isolation techniques on the physico-chemical and thermal properties of cellulose nanowhiskers (CNW) from oil palm biomass obtained microcrystalline cellulose (MCC). Fourier transform infrared analysis showed that there are no significant changes in the peak positions, suggesting that the treatments did not affect the chemical structure of the cellulose fragment. Scanning electron microscopy showed that the aggregated structure of MCC is broken down after treatment. Transmission electron microscopy revealed that the produced CNW displayed a nanoscale structure. X-ray diffraction analysis indicated that chemical swelling improves the crystallinity of MCC while maintaining the cellulose I structure. Acid hydrolysis however reduced the crystallinity of MCC and displayed the coexistence of cellulose I and II allomorphs. The produced CNW is shown to have a good thermal stability and hence is suitable for a range of applications such as green biodegradable nanocomposites reinforced with CNW.

In this chapter, the effects of micro- and nano-cellulose; microcrystalline cellulose (MCC) and cellulose nanowhiskers (CNW), on the properties of montmorillonite (MMT)/polylactic acid (PLA) nanocomposites fabricated using solution casting method were investigated. CNW were isolated from MCC using a chemical swelling method. An initial study showed that the optimum MMT content, based on tensile properties, in PLA/MMT nanocomposite is 5 phr (parts per hundred parts of resin). PLA/MMT/MCC hybrid composites and PLA/MMT/CNW hybrid nanocomposites were produced by incorporating of various contents of MCC and CNW into the optimum formulation of PLA/MMT nanocomposites (P/MT5), respectively. The Young’s modulus of PLA/MMT/MCC hybrid composites and PLA/MMT/CNW hybrid nanocomposites increased gradually with increasing MCC and CNW content, respectively. The tensile strength of hybrid composites decreased compared to P/MT5 nanocomposite. However, the tensile strength for the hybrid nanocomposites increased with incorporation of CNW and reached the highest value at 1 phr CNW content. The ductility of hybrid composites and hybrid nanocomposites was also increased significantly from ~10 to ~60 and ~90 % with the incorporation of 1 phr MCC and CNW fillers, respectively. This increase in ductility was proposed to be due to the nucleation of crazes and the formation of shear bands in the PLA. Transmission electron microscopy and X-ray diffraction analyses showed that MCC slightly decreased the MMT interlayer spacing in hybrid composites, while the MMT interlayer spacing in hybrid nanocomposites increased by incorporation of CNW into P/MT5 nanocomposite.

A feeding trial was conducted for 49 days to evaluate the effect of partially substituting fishmeal with fermented prawn waste liquor (FPWL) in juvenile sea bass diets at 10%, 20%, and 30% of the total diet. Growth performance of sea bass from 16 g up to 40 g fed with FPWL-supplemented diet was not significantly different from the all fishmeal control diet. The most cost-effective diet included FPWL at 30%, with weight gain, feed conversion ratio, and protein efficiency ratio of 180%, 1.78%, and 1.2% respectively.

Cellulose nanowhiskers are lightweight, inexpensive, biocompatible nanomaterials that have found wide range of applications. One of their important applications is in the development of reinforced polymer nanocomposites (PNC). The aim of this study was to isolate cellulose nanowhiskers from oil palm biomass microcrystalline cellulose (MCC) using chemical swelling treatment. Analysis of Fourier transform infrared spectroscopy (FTIR) indicated that chemical swelling did not change the chemical structure of the cellulosic fragments. The morphology of the swelled MCC was observed using scanning electron microscopy (SEM) and the micrographs showed that the aggregated structure of MCC have broken down. The produced cellulose nanowhiskers (CNW-S) were estimated to have less than 20 nm width and lengths of 300 nm after treatment, which confirm its nanoscale structure. X-ray diffraction analysis indicated that chemical swelling improve slightly the crystallinity of MCC while maintaining the cellulose I structure. Thermogravimetric analysis (TGA) showed that the CNW-S was significantly thermally more stable than MCC, having higher on-set degradation temperature and maximum degradation temperature.

The aim of this work was to evaluate the effects of hexavalent chromium [Cr(VI)] addition at different growth phases on the Cr(VI) reducing capacity of the aerobic Gram-negative bacterium, Acinetobacter haemolyticus. The addition of 10–100 mg Cr(VI) L−1 as potassium dichromate at the time of inoculation (T0) resulted in the extension of time needed to reach the stationary phase, with a total growth inhibition at 70 mg Cr(VI) L−1, a decrease in bacterial count from 108 to 102 CFU mL−1, and a Cr(VI) reduction drop to 35% at 100 mg Cr(VI) L−1. However, bacterial growth was uninterrupted when 10–100 mg Cr(VI) L−1 were added at the early stationary phase (after 12 h of bacterial growth) indicated by a high bacterial count of 108 CFU mL−1. More than 95% of Cr(VI) was reduced at an initial Cr(VI) of 50 mg L−1. However, the Cr(VI) reduction capacity dropped to 50% at 100 mg Cr(VI) L−1. This study showed that the ability of Acinetobacter haemolyticus to reduce Cr(VI) depends strongly on the number of surv...

Acinetobacter haemolyticus, a Gram-negative aerobic locally isolated bacterium, immobilized on wood-husk showed the ability to detoxify Cr(VI) to Cr(III). Wood-husk, a natural cellulose-based support material, packed in an upward-flow column was used as support material for bacterial attachment. Around 97% of the Cr(VI) in wastewater containing 15 mg L(-1) of Cr(VI) was reduced at a flow rate of 8.0 mL min(-1). The wastewater containing Cr(VI) was added with liquid pineapple wastewater as nutrient source for the bacteria. Electron microscopic examinations of the wood-husk after 42 days of column operation showed gradual colonization of the wood-husk by bacterial biofilm. The use of 0.1% (v/v) formaldehyde as a disinfecting agent inhibited growth of bacteria present in the final wastewater discharge. This finding is important in view of the ethical code regarding possible introduction of exogenous bacterial species into the environment.

Natural fibers from agricultural wastes are finding their importance in the polymer industry due to the many advantages such as their light weight, low cost and being environmentally friendly. Rice husk (RH) is a natural sheath that forms around rice grains during their growth. As a type of natural fiber obtained from agroindustrial waste, RH can be used as filler in composites materials in various polymer matrices. This review paper is aimed at highlighting previous works of RH filled polymer composites to provide information for applications and further research in this area. Based on the information gathered, application of RH filled composites as alternative materials in building and construction is highly plausible with both light weight and low cost being their main driving forces. However, further investigations on physical and chemical treatment to further improve the interfacial adhesion with polymeric matrix are needed as fiber-polymer interaction is crucial in determining the final composite properties. Better understanding on how the used polymer blends as the matrix and secondary fillers may affect the properties would provide interesting areas to be explored.

Effective microorganisms or EM has been actively used for various reasons but mainly in the waste water treatment, as plant growth initiators and fertilizers. In this study, fermentations of local tiger prawn waste (Panaeus monodon) by EM were conducted at laboratory scale at different fermentation conditions for protein recovery. Fermentations were conducted at various temperature conditions (250C, 370C and 600C) and various level of inoculum and carbohydrate source (5%, 10%, 15% and 20%) and their pH values compared over 72 hours. Results showed that the pH rapidly decreased to pH 5.0 and the fermentation profiles were similar when different types of carbohydrates were used during fermentation. However, temperatures affect fermentations considerably where the pH did not rapidly decrease at 600C. The fermentation products or silage formed is also stable over a period of 60 days. In addition, acid production was dependent on glucose concentration but not on the inoculum level. For protein production, approximately 86% of protein can be recovered after fermentation process. Therefore, it can be suggested that fermentations were successful using EM on palm brown sugar and fermentation done at either 250C or 370C due to its better acid production.

Treatment of minced scampi (Nephrops norvegicus) waste, supplemented with glucose, in a bioreactor by a culture of the lactic acid bacterium, Lactobacillus paracasei strain A3, is described. The bioreactor comprised a mesh-covered basket mounted horizontally and enclosed within a glass outer jacket. The minced waste was placed inside the basket and agitation was provided by the controlled rotation of the basket. Batch fermentation was conducted over a period of 5 days at a temperature of 30°C, during which a protein-rich liquor was produced as a result of proteolysis. The pH of this liquor attained a value of 5·0 after a period of approximately 48 h, and under these conditions rapid solubilisation of calcium from the shell components of the waste occurred. At the end of the fermentation, the solid fraction comprised 17·5% chitin (dry weight basis) with, respectively, 77·5 and 61·0% of protein and calcium present in the initial waste material having been solubilised. The by-product liquor may have potential as an animal feed supplement.

In this work, polylactic acid (PLA) composites filled with microcrystalline cellulose (MCC) from oil palm biomass were successfully prepared through solution casting. Fourier transform infrared (FT-IR) spectroscopy indicates that there are no significant changes in the peak positions, suggesting that incorporation of MCC in PLA did not result in any significant change in chemical structure of PLA. Thermogravimetric analysis was conducted on the samples. The T50 decomposition temperature improved with addition of MCC, showing increase in thermal stability of the composites. The synthesized composites were characterized in terms of tensile properties. The Young's modulus increased by about 30%, while the tensile strength and elongation at break for composites decreased with addition of MCC. Scanning electron microscopy (SEM) of the composites fractured surface shows that the MCC remained as aggregates of crystalline cellulose. Atomic force microscopy (AFM) topographic image of the composite surfaces show clustering of MCC with uneven distribution.

Poly (lactic acid) (PLA)/chitosan (CS) natural polymer/epoxidised natural rubber (ENR) composites were successfully prepared through a solution casting method. The morphological characteristics of fabricated composites were investigated by scanning electron microscopy (SEM) and optical microscopy. The microstructure of PLA/ENR was significantly altered with the addition of CS. SEM analysis of composites fractured surfaces revealed smooth and homogeneous texture and good dispersion of CS. However for 15 wt% CS composites, the phase segregation and poor adhesion between the polymers were observed. Fourier transform infrared spectroscopy revealed some levels of attractive interaction between CS, PLA, and ENR in the composites. The mechanical properties of composites in terms of tensile strength and tensile modulus were significantly improved with the addition of CS into the matrix while the percent elongation at break decreased. The tensile strength increased up to 5 wt% CS loading for both PLA/CS and PLA/ENR/CS and thereafter decreased while Young’s modulus increased up to 10 wt%. However, when the CS content was increased to 15 wt%, the tensile strength and tensile modulus were slightly decreased. These improvements were attributed to good dispersion of CS at the optimum filler levels and attractive interaction between the composites components.

In this study, the ability of chitosan-immobilized Acinetobacter haemolyticus as biosorbent for chromium (VI) biosorption in batch system was investigate. Optimized parameter namely pH, contact time, biosorbent dosage and initial metal concentration obtained from the experiment was then applied for electroplating wastewater treatment. Biosorption using chitosan-immobilized Acinetobacter haemolyticus at pH 3, 8 hours contact time, 3% (w/v) of biosorbent dosage with 100 mg L−1 initial metal concentration resulted in maximum chromium (VI) uptake of 0.2 mg g−1. Using electroplating wastewater, the biosorption capacity of the chitosan immobilized Acinetobacter haemolyticus was 0.27 mg g−1 at pH 3 which is higher than unmodified pH.

The bacterial reduction of Cr(VI) from industrial wastewater was evaluated using a 2.0-m(3) bioreactor. Liquid pineapple waste was used as a nutrient for the biofilm community formed inside the bioreactor. The use of rubber wood sawdust as packing material was able to immobilize more than 10(6) CFU mL(-1) of Acinetobacter haemolyticus cells after 3 days of contact time. Complete reduction of 15-240 mg L(-1) of Cr(VI) was achieved even after 3 months of bioreactor operation. Cr(VI) was not detected in the final effluent fraction indicating complete removal of Cr from solution from the flocculation/coagulation step and the unlikely re-oxidation of Cr(III) into Cr(VI). Impatiens balsamina L. and Gomphrena globosa L. showed better growth in the presence of soil-sludge mixture compared to Coleus scutellarioides (L.) Benth. Significant amounts of Cr accumulated at different sections of the plants indicate its potential application in Cr phytoremediation effort. The bacterial-based system was also determined not to be detrimental to human health based on the low levels of Cr detected in the hair and nail samples of the plant operators. Thus, it can be said that bacterial-based Cr(VI) treatment system is a feasible alternative to the conventional system especially for lower Cr(VI) concentrations, where sludge generated can be used as growth supplement for ornamental plant as well as not detrimental to the health of the workers.

A lipolytic Pseudomonas sp. has been successfully immobilized in strontium alginate gel bead for use in the production of lipase. This paper reports on the various conditions required for its optimum production. A 3% alginate gel concentration with a 20% (w/v) cell loading gives the highest production of lipase. The production of lipase can be enhanced by aeration and shaking but mass transfer effect may be dependent on the ratio of cell mass and bead size. Prolonged recycling with aeration accelerates the rupturing of the beads compared to non-aerated system. A maximum production of lipase is given by 1.5g of immobilized bacteria in 50ml of culture broth. The immobilized bacteria can withstand recycling up to 24 days, (72h cycle), after which time the beads ruptured. The production, however, remains at 70%.

Possible application of a locally isolated environmental isolate, Acinetobacter haemolyticus to remediate Cr(VI) contamination in water system was demonstrated. Cr(VI) reduction by A. haemolyticus seems to favour the lower concentrations (10–30 mg/L). However, incomplete Cr(VI) reduction occurred at 70–100 mg/L Cr(VI). Initial specific reduction rate increased with Cr(VI) concentrations. Cr(VI) reduction was not affected by 1 or 10 mM sodium azide (metabolic inhibitor), 10 mM of PO43−, SO42−, SO32−, NO3− or 30 mg/L of Pb(II), Zn(II), Cd(II) ions. However, heat treatment caused significant dropped in Cr(VI) reduction to less than 20% only. A. haemolyticus cells loses its shape and size after exposure to 10 and 50 mg Cr(VI)/L as revealed from TEM examination. The presence of electron-dense particles in the cytoplasmic region of the bacteria suggested deposition of chromium in the cells.

Acid hydrolysis method was used to isolate microcrystalline cellulose (MCC) from oil palm empty fruit bunches (OPEFB) total chlorine free bleached pulp. The derived MCC was incorporated into polylactic acid (PLA) using solution casting technique in order to produce PLA/MCC composites. The chemical structure of the cellulose fragments remains unaltered as demonstrated by Fourier transform infrared spectroscopy despite acid hydrolysis. X-ray diffraction showed that the MCC has a cellulose I polymorph with 87% crystallinity index. The addition of MCC into PLA enhanced not only the thermal stability but also the Young's modulus of the PLA/MCC composites by approximately 30% at 5 phr MCC contents compared to pure PLA. However a decrease in tensile strength and elongation at break of the PLA/MCC composites were observed due to the poor dispersion of MCC in the PLA matrix

The effect of the degree of deacetylation of chitosan on the chemical structure, thermal properties, and compatibility of chitosan/polyamide66 (CS/PA66) blends were investigated. Blends of CS with PA66 were prepared via the solution casting technique by using 85% formic acid. Structural interaction between PA66, CS, and CS/PA66 blends were analyzed by infrared spectroscopy. FT-IR spectra showed displacement of the carbonyl band of the amide group of chitosan toward smaller wave numbers, indicating possible existence of hydrogen bonding between the two macromolecules. Thermal and morphological behavior of films containing chitosan with degree of deacetylation (DD) ranging from 52.9% to 85% in the polymer blends were investigated by thermogravimetric analysis and scanning electron microscopy. Thermal analysis showed that the CS/PA66 blends became more thermally stable than pure chitosan. The morphological behavior observed by scanning electron microscopy indicated phase segregation in all types of blending. Acetyl content in chitosan was found to influence the degree of compatibility. Decreasing the acetyl group or increasing the DD of chitosan increases the compatibility of the CS/PA66 blends.