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Microbial electrolysis cells (MECs) are a new bio-electrochemical method for converting organic matter to hydrogen gas (H2). Palm oil mill effluent (POME) is hazardous wastewater that is mostly formed during the crude oil extraction process in the palm oil industry. In the present study, POME was used in the MEC system for hydrogen generation as a feasible treatment technology. To enhance biohydrogen generation from POME in the MEC, an empirical model was generated using response surface methodology (RSM). A central composite design (CCD) was utilized to perform twenty experimental runs of MEC given three important variables, namely incubation temperature, initial pH, and influent dilution rate. Experimental results from CCD showed that an average value of 1.16 m3 H2/m3 d for maximum hydrogen production rate (HPR) was produced. A second-order polynomial model was adjusted to the experimental results from CCD. The regression model showed that the quadratic term of all variables tested had a highly significant effect (P

Thraustochytrids, such as members of the genus Aurantiochytrium, are rich in docosahexaenoic acid (DHA, C22:6n-3) and represent a promising source of omega-3 fatty acids which plays a vital role in the enhancement of human health, particularly for neurological and visual functions. Different modes of cultivation (batch, fed-batch and repeated-batch) by Aurantiochytrium sp. SW1 were studied for effective docosahexaenoic acid (DHA) production. In this study, three different modes of fermentation were carried out in 1 L shake flasks with a working volume of 500 mL, incubated at 30 ºC and 200 rpm. Batch cultivation significantly exceeds the rest of cultivation modes, achieving maximal lipid and DHA concentrations of 11.22 g/L and 5.87 g/L, respectively, and DHA productivity of 0.061 g/L/h. Lipid and DHA concentration of the repeated-batch process decreased through the cycles for all three different types of replacement ratio (80, 90 and 95%). The average decrease percentage of DHA concentration for cycle one and cycle two were 21.76 and 32.52%, respectively. However, the fatty acid composition of lipids obtained in the cycles remained consistent with 16:0 and DHA being the most abundant fatty acids indicating that this mode of fermentation is highly useable for industrial applications.

The synthesis of PANI incorporated with Ag-Fe in nanocomposite thin films-based electrochemical sensor was developed by irradiating with 10 kGy dose of gamma ray. PANI-Ag-Fe nanocomposite was synth...

Bioacetone, biobutanol, and bioethanol (BioABE) production is dependent on the fermentable sugars produced from lignocellulosic biomass and on the composition and initial pH of the medium. Understanding these process variables and their interconnectedness could enhance the BioABE product yield. Acacia mangium is available abundantly and it is a potential feedstock for BioABE production. In this study, BioABE was produced from fermentable sugars of A. mangium using Clostridium acetobutylicum YM1. Alkaline treated A. mangium (70 °C, 3 h, 5.50 %w/v NaOH) was further hydrolyzed via enzymatic hydrolysis using a multi-enzyme of white rot fungi to convert it into fermentable sugars. Approximately 15 g/L of fermentable sugars was produced from A. mangium (100 g/L) and was used for BioABE production in comparison with glucose. Initial findings showed that only 0.94 g/L of BioABE was produced in comparison with glucose (2.86 g/L) at a pH of 6.2. Decreasing the initial pH of the medium to 4.50 increased the BioABE (2.87 g/L), and after the medium was supplemented with tryptone-yeast-acetate (TYA), the BioABE yield increased by more than 100% to 6.84 g/L. This study discovered that BioABE produced from A. mangium was comparable to using commercial glucose, thus offering high potential as a low-cost feedstock.

The key enzymes of lipid biosynthesis in oleaginous filamentous fungi exist as metabolons. However, the existence of a similar organization in other groups of oleaginous microorganisms is still unknown. In this study, we confirmed the occurrence of two separate and distinct lipogenic metabolons in a thraustochytrid, Aurantiochytrium SW1. These involve the Type I Fatty Acid Synthase (FAS) pathway, consisting of six enzymes: fatty acid synthase, malic enzyme (ME), ATP: citrate lyase (ACL), acetyl-CoA carboxylase (ACC), malate dehydrogenase (MD) and pyruvate carboxylase (PC), and the Polyketide Synthase-like (PKS) pathway, consisting of PKS subunits a, b, c, glucose-6-phosphate dehydrogenase (G6PDH) 6-phosphogluconate dehydrogenase (6PGDH), ACL and ACC. This suggests that the NADPH requirement for the FAS pathway is primarily generated and channelled by ME whereas G6PDH and 6PGDH fulfil this role for the PKS pathway. Diminished biosynthesis of palmitic acid (16:0), docosahexaenoic acid (22:6 n-3, DHA) and docosapentaenoic acid (22:5 n-6, DPA) correlated with the dissociation of their respective metabolons thereby suggesting that regulation of the pathways is achieved through the formation and dissociation of the metabolons.

Thraustochytrids, such as

Aurantiochytrium sp., a fungoid marine protist that belongs to Stramenophila has proven its potential in the production of polyunsaturated fatty acids (PUFAs), especially docosahexaenoic acids (DHA). In this study, genomic characterisation of a potential producer for commercial production of DHA, Aurantiochytrium sp. SW1 has been carried out via whole genome sequencing analysis. The genome size of this strain is 60.89 Mb, with a total of 11,588 protein-coding genes. Among these, 9,127 genes could be functionally annotated into a total of 7,248 (62.5 %) from UniProt, 6,554 (56.6 %) from KEGG and 8,643 (74.6 %) genes from eggNOG protein database. The highest proportion of genes belongs to the protein family of metabolism were further assigned into 11 metabolic categories. The highest number of genes belonging to lipid metabolism (321 genes) followed by carbohydrate metabolism (290 genes), metabolism of cofactors and vitamins (197 genes) and amino acid metabolism (188 genes). Further analysis into the biosynthetic pathway for DHA showed evidence of all genes involved in PKS (polyketide synthase)-like PUFA synthase pathway and incomplete fatty acid synthase-elongase/desaturase pathway. Analysis of PUFA synthase showed the presence of up to ten tandem acyl carrier protein (ACP) domains which might have contributed to high DHA production in this organism. In addition, a hybrid system incorporating elements of FAS, Type I PKS and Type II PKS systems were found to be involved in the biosynthetic pathways of fatty acids in Aurantiochytrium sp. SW1. This study delivers an important reference for future research to enhance the lipid, especially DHA production in Aurantiochytrium sp, SW1 and establishment of this strain as an oleaginous thraustochytrid model.

Aims: We aimed to develop a high-throughput lectin assay with minimized background signals to investigate the interactions of lectins and sialic acid glycans, focusing on Prostate- Specific Antigen (PSA). Background: High background signals resulting from nonspecific binding are a significant concern for microtiter plate-based Enzyme-Linked Lectin Sorbent Assays (ELLSAs), as they can mask specific binding signals and cause false-positive results. Methods: In this study, we constructed an ELLSA based on different washing step parameters, including the number of washing cycles, NaCl and Tween-20 concentrations, and the type of blocking agent and evaluated the effects on both specific and nonspecific binding signals. Furthermore, we performed a PSA binding assay using the optimized ELLSA. Results: The optimal washing parameters based on the highest specific binding signal proposed four cycles of washing steps using a washing buffer containing a high salt concentration (0.5 M NaCl) and mild detergent (0.05% Tween-20). The utilization of the optimized washing parameters in this assay was shown to be sufficient to obtain the optimal binding signals without the use of any blocking agent. Binding assays performed using the optimized ELLSA revealed that the glycan of the PSA sample used in this study mainly consists of terminal α2,6-linked sialic acid, as strongly recognized by Sambucus nigra agglutinin (SNA) with a KD value of 12.38 nM. Conclusion: The ELLSA reported in this study provides a simple yet sensitive assay for sialic acid linkage recognition.

Thraustochytrids are getting increasingly popular due to their high potential role as alternative producers of the high-valued ω-3 polyunsaturated fatty acids (PUFA), docosahexaenoic acid (DHA). While most thraustochytrids prefer glucose as the major carbon source, few strains have been reported to prefer fructose. One such strain is Aurantiochytrium sp. SW1. In this study, the effect of fructose on DHA accumulation by SW1 was investigated using a two-level full factorial design. Besides, biomass, lipid and DHA accumulation profiles of SW1 cultivated in fructose and glucose media were compared. Results revealed that fructose has a very significant positive effect on the volumetric DHA content. Meanwhile, its involvement in affecting DHA biosynthetic capacity, though significant, is not very profound. It was also found that when cultivated in fructose medium, SW1 had a less steep log phase compared to that of glucose medium. However, after 48h of cultivation, biomass and lipid accumulation in fructose medium outweighed the other. Volumetric DHA content in fructose medium at 96h was 11% higher than that of glucose medium. Overall, fructose was found to be a more suitable substrate for biomass, lipid and DHA accumulation in SW1 compared to the conventional source, glucose., thraustochytrids, fructose, factorial design, docosahexaenoic acid (DHA).

This study employed Bacillus spp. with α-amylase production isolated from Malaysian hot spring for domestic kitchen food waste treatment contained grains, vegetables, chicken and tuna that mimic the food waste discharge from domestic kitchens in Malaysian household. Results showed that Bacillus licheniformis HULUB1 and Bacillus subtilis SUNGB2 possess excellent amylolytic properties. Highest α-amylase activity was obtained when both isolates were cultivated at pH 6.0 and 65 °C with concentrations of 18.15 U/mL for HULUB1 and 22.14 U/mL for SUNGB2. Stability of α-amylase with significant levels of enzyme activity were recorded at 55-85 °C and pH 5.0-9.0. The extracted mixed α-amylase of HULUB1 and SUNGB2 showed greatest reduction were achieved at day 12 with 45% ± 0.03 solid content at 65 °C. While the mixed culture of HULUB1 and SUNGB2 displayed an enhanced effect on the food waste contents reduction with 43% ± 0.02 solid content at 45 °C after day 12. The findings showed that the combination of the two Bacillus spp. isolates possessed degradation of food wastes at faster rate than α-amylase. It was also pointed out that the standard food waste (SFW) and the treatment process assimilated for this study was suitable for the growth of Bacillus spp.

In the present study, the impact of eight phytohormones from six different classes on the growth, lipid and docosahexaenoic acid (DHA) biosynthetic capacity of Aurantiochytrium sp. SW1 (SW1) was evaluated. Kinetin (KIN), jasmonic acid (JA) and gibberellic acid (GA) significantly enhanced the growth and DHA production of SW1 by 16%&ndash, 28% and 66%&ndash, 84% in comparison to the control, respectively. The synergistic effect of these three phytohormones, evaluated by the response surface methodology (RSM), showed that a combination of 3.6 mg/L GA, 2.0 mg/L KIN and 20.0 mg/L JA further increased the growth and DHA production of SW1 by 16% to 28% and 22% to 36%, respectively, in comparison to the individual supplementation. The synergistic effect of these phytohormones was also shown to be time-dependent, where feeding at 24 h of cultivation led to 15%, 26% and 35% further increments in the biomass, lipid and DHA production in comparison to that of 0 h, respectively. The determination of stress markers, antioxidant enzymes and key enzymes involved in fatty acid biosynthesis aided to elucidate the potential mechanism underlying the improvement of growth and DHA production by SW1 at various times of feeding. Supplementation with the phytohormones at 24 h exhibited the maximum impact on reducing the level of reactive oxygen species (ROS) and malondialdehyde (MDA), as well as augmented the antioxidants (superoxide dismutase and catalase) and key metabolic enzymes involved in lipogenesis (malic, glucose-6-phosphate dehydrogenase and ATP-citrate lyase) in comparison to the control and other time points. This study signifies the potential application of phytohormones for improving the growth, lipid and DHA production in Aurantiochytrium spp.

The microbial electrolysis cell (MEC) is a novel biotechnological process that can translate the chemical energy (organics/nutrients) present in wastewater or biomass into hydrogen gas and other valuable products. For the realization of real-world MEC application, achieving optimal hydrogen production is necessary. To obtain this optimum hydrogen production, significant factors about the MECs must be realized. Therefore, in this chapter, key factors affecting H2 production and yield in MECs are explored and the important factors are fully discussed. The performance of an MEC depends on many factors and operating parameters: the types of microorganisms and their metabolic behavior, anodic e− (electron) transport and its mechanism, energy sources (substrate, fuel, nutrients), physiochemical properties of electrode and membrane materials, various separators, operating parameters such as pH, temperature (T), Eap (applied voltage), or external power source, organic loading rate, conductivity, and the salinity or ionic strength of electrolytes and solutions are considered to be the critical parameters. The geometric design of MECs reactors is also considered to include influencing parameters. Overall, advances in MEC technology in terms of operating costs, substrates, and use of low-cost electrode materials are required to make MEC systems sustainable, economical, and a commercially viable technology.

Microalgae are often considered unique due to their diverse growth requirements, leading to their capability to produce miscellaneous useful products such as carbohydrates, proteins, lipids, and other bioactive molecules. Microalgal-lipids, also known as microalgae-single cell oil (MSCO), have attracted considerable interest worldwide, due to their extensive potential applications in the renewable energy, biopharmaceutical, and nutraceutical industries. Most autotrophic and mixotrophic microalgae are often studied as potential fuel stocks owing to their high photosynthetic efficiency and ability to produce an excellent source of neutral lipids. In addition, some microalgae are capable of producing long-chain polyunsaturated fatty acids (LC-PUFAs) such as DHA, DPA, and EPA, as they use not only the conventional Fatty Acid Synthase (FAS) pathway but also a unique fatty acid biosynthesis mechanism known as polyketyl synthase (PKS) which is commonly absent in most oleaginous microbes. Although MSCO is a feasible source for bioenergy and biopharmaceuticals in general, some limitations and challenges remain, which must be overcome to upgrade the technology from pilot-phase to industrial level. The present review comprehensively discuss the background, cultivation systems, regulatory mechanism in fatty acids biosynthesis, its useful products, and the challenges for commercial-level applications.

Microbial electrolysis cell (MEC) is a promising and relatively newer bioelectrochemical process for sustainable H2, value-added compounds production, and simultaneous wastewater treatment. As compared to other alternative technologies, the MEC has shown numerous strengths: primarily, the MECs pledge the feasibility to generate H2 at proportionately less energy consumption than the usual energy demand for water electrolysis. In addition, MECs are not restricted by dark fermentation (DF) barriers; H2 could be completely extracted from the spent medium in MECs, achieving remarkable H2 recovery than all kinds of processes. What is more, significantly pure H2 is generated in the MECs cathodes. Besides, MECs incorporate both treatment of waste and bioenergy generation, thereby the MEC possesses the benefits of being environmentally friendly, efficient, and waste disposal. Also, MEC has the ability to produce a wide variety of value-added products, such as methane, hydrogen peroxide, ethanol, and so on, and all these attracted enormous attention in both academia and industry. The MEC must be robust enough to be used in the field for bioremediation or energy production.

The use of Ag–Pd bimetallic nanoparticles was reported as an enhanced sensing material in electrochemical sensing application. The composite of bimetallic nanoparticles with conducting polymer has attracted an interest in microbial sensor. Ag–Pd bimetallic nanoparticles embedded in polyaniline (PANI) system was synthesized using sol–gel method and deposited on glass substrate by spin coating technique with various concentrations of Ag and Pd. The films properties were studied using XRD, TEM and AFM to analyze the internal structure and surface morphology. Sensor performance was carried out using current–voltage (I–V) measurement and electrochemical impedance spectroscopy (EIS) to monitor the presence of Escherichia coli bacteria in liquid medium. From XRD analysis, the face-centered cubic of Ag–Pd bimetallic crystal were found at lattice (1 1 1) and (2 0 0). The crystallite size and lattice parameter were found to be decrease as concentration of Pd increased. TEM analysis shows the particles of Ag–Pd bimetallic in spherical shape with 10–20 nm in diameter. AFM analysis show the surface roughness of PANI–Ag–Pd thin films decrease as the concentration of Pd increased. From I–V and EIS analysis, the prototype sensor of PANI–Ag–Pd nanocomposite thin films performed well with high sensitivity when Pd concentration is increasing.

The effect of pH and butyric acid supplementation on the production of butanol by a new local isolate of Clostridium acetobutylicum YM1 during batch culture fermentation was investigated. The results showed that pH had a significant effect on bacterial growth and butanol yield and productivity. The optimal initial pH that maximized butanol production was pH 6.0 ± 0.2. Controlled pH was found to be unsuitable for butanol production in strain YM1, while the uncontrolled pH condition with an initial pH of 6.0 ± 0.2 was suitable for bacterial growth, butanol yield and productivity. The maximum butanol concentration of 13.5 ± 1.42 g/L was obtained from cultures grown under the uncontrolled pH condition, resulting in a butanol yield ( Y P / S ) and productivity of 0.27 g/g and 0.188 g/L h, respectively. Supplementation of the pH-controlled cultures with 4.0 g/L butyric acid did not improve butanol production; however, supplementation of the uncontrolled pH cultures resulted in high butanol concentrations, yield and productivity (16.50 ± 0.8 g/L, 0.345 g/g and 0.163 g/L h, respectively). pH influenced the activity of NADH-dependent butanol dehydrogenase, with the highest activity obtained under the uncontrolled pH condition. This study revealed that pH is a very important factor in butanol fermentation by C. acetobutylicum YM1.

Malic enzyme (ME) plays a vital role in determining the extent of lipid accumulation in oleaginous fungi being the major provider of NADPH for the activity of fatty acid synthase (FAS). We report here the first direct evidence of the existence of a lipogenic multienzyme complex (the lipid metabolon) involving ME, FAS, ATP: citrate lyase (ACL), acetyl-CoA carboxylase (ACC), pyruvate carboxylase (PC) and malate dehydrogenase (MDH) in Cunninghamella bainieri 2A1. Cell-free extracts prepared from cells taken in both growth and lipid accumulation phases were prepared by protoplasting and subjected to Blue Native (BN)-PAGE coupled with liquid chromatography–tandem mass spectrometry (LC-MS/MS). A high molecular mass complex (approx. 3.2 MDa) consisting of the above enzymes was detected during lipid accumulation phase indicating positive evidence of multienzyme complex formation. The complex was not detected in cells during the balanced phase of growth or when lipid accumulation ceased, suggesting that it was transiently formed only during lipogenesis.

Microbial electrolysis cell (MEC) is a promising method for hydrogen production by microorganisms. The culture conditions were optimized for Geobacter sulfurreducens PCA ATCC 51573 using response surface methodology involving central composite design (CCD). Effects of sodium bicarbonate, sodium acetate, sodium fumarate, incubation temperature, and initial pH value of culture on cell growth of G. sulfurreducens PCA ATCC 51573 were studied. Experimental data obtained from CCD were utilized to generate a second-order polynomial regression model and to evaluate the effect of the variables studied on the optical density (OD) as the main response of bacterial growth of the strain PCA ATCC 51573. The statistical analysis showed that sodium bicarbonate, sodium acetate, and sodium fumarate had significant effect on OD value (P

Present day, the environmental issues and the insufficiency of energy supply are of major concerns around the world. In view of this, numerous utilities have interchanged their production sources and path ways to green and renewable energy. The hydropower (HP) is the world's largest and the most efficient sustainable way to produce electricity or power. Nowadays, HP is employed for converting 90% of the energy of moving water into electricity/power. This can be comparable to the fossil fuels (FFs) based power plants, which are maximum only 60% efficient. The high expenditure and adverse environmental concerns that associated with the use of large HP plants have helped to focus the attention on small or Pico-scale HP plants, which reduce these affects considerably. Pico hydropower (PHP) offers an efficient, reliable and cost effective of alternative power sources. In addition, the demand for PHP in the market shows that PHP is the best and low-priced choice for rural or remote area electrification in developing nations. Nevertheless, the PHP technology is still considered as a brand-new in Malaysia. In this paper, the basic theories or concept of PHP were described for better understanding and recognition on this type of electricity or power production system. Furthermore, present status and projected future of PHP in Malaysia, inclusive of current installed capacity and potential of PHP energy resources are discussed. Besides that, the paper presents the barriers that hinder the proliferation of PHP in the Malaysia, the great challenges and outlooks for future developments of the PHP in Malaysia. By and large, the objective is to provide essential strategic implications for Malaysia and other Southeast Asian countries.

Fermenting palm kernel cake (PKC) hydrolysate using C.acetobutylicum YM1 produces butanol. Firstly, PKC is exposed to acid pretreatment to release fermentable sugars. Besides sugar, PKC hydrolysate consists of a mixture of microbial inhibitors. Sulfuric acid-treated PKC (2% SAPKC) released 30 g/L of reducing sugars. The concentration of microbial inhibitors are measured and two decontamination techniques namely overliming and activated charcoal are used and studied for their effectiveness in decreasing the microbial inhibitors and thereby increase the production of butanol. The activated charcoal detoxification technique produced good results in decreasing furan aldehydes compounds compared to overliming method. Even though overliming method decreased the inhibitory elements, the end amount of butanol produced is comparatively lower than the non-detoxified SAPKC. Activated charcoal technique increased productivity and yield of acetone, butanol, and ethanol (ABE).

A statistical design approach has been used to optimize the production of biomass byCunninghamellasp. 2A1, evaluated based on lipidless biomass. A 23full factorial centralcomposite design (CCD) was chosen to study the combined effects of three factors; ammoniumtartrate, peptone and glucose concentrations. The p-value for each factors was < 0.05 suggestingthat these factors have significant effect on the production of lipidless biomass. The productionis represented by a linear model with p-value < 0.0001. The optimized medium consists of 3.86g/l ammonium tartrate, 55.84 g/l glucose and 7.73 g/l peptone predicted 16.83 g/l lipidlessbiomass. Results from four replications based on the optimized medium produced 18.48 g/llipidless biomass, which are in close agreementwith the predicted value. The coefficient forglucose was the highest indicating it as the most significant factoraffecting lipidless biomassproduction.

A kinetic model of bacterial growth and metabolite production can adequately explain the trends and interaction of important parameters in a fermentation process. Production of surfactin by two bacterial strains, namely, Bacillus subtilis MSH1 and Bacillus subtilis ATCC 21322, in a 5 L bioreactor was investigated using Cooper’s media with 4% (v/v) glucose. The present kinetic study was carried out in order to determine the correlation between microbial cell growth, surfactin production and glucose consumption. Batch fermentation was performed by cultivation of each selected strain in a bioreactor at 30°C for 55 h. The experimental results showed production of surfactin in the culture medium after 5 and 10 h of incubation for B. subtilis ATCC 21332 and B. subtilis MSH1, respectively, at which the bacterial cells were at an early stage of the log phase. The maximum concentration of surfactin (Pmax) achieved by B. subtilis MSH1 and B. subtilis ATCC 21332 was 226.17 and 447.26 mg/L, respectively. The kinetic study of bacterial cell growth of both strains indicated that B. subtilis MSH1 had a specific growth rate (μmax) of 0.224 h-1 and attained a maximum biomass concentration (Xmax) as high as 2.90 g/L after 28 h of fermentation, while B. subtilis ATCC 21332, with μmax of 0.087 h-1, attained an Xmax of 2.62 g/L after 45 h of incubation. B. subtilis MSH1 showed higher growth kinetics, thus exhibited higher values of μmax and Xmax compared with B. subtilis ATCC 21332 under identical fermentation conditions. The Pmax achieved by B. subtilis ATCC 21332 was 447.26 mg/L, two times higher than that achieved by B. subtilis MSH1 (226.17 mg/L). The results obtained provide kinetics information including values of Pmax, μmax and Xmax for better understanding of interactions of bacterial cell growth and glucose consumption towards surfactin production by a commercial strain of B. subtilis ATCC 21332 and a local isolate of B. subtilis MSH1.

The fabricated E. coli sensor of ZnO-rGO nanocomposite thin films by gamma radiation was investigated. Nanocomposite films were prepared via sol–gel method and were irradiated at 10 kGy at room temperature. The surface characteristic of as-prepared samples have been characterized by x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The proposed structure shows that exposed gamma radiation may change the microstructure of the films occurs as a result of their flexible structure. Uv–vis spectra of nanocomposite were studied to investigate the optical behavior of ZnO-rGO films and the optical energy band gap and Urbach energy were found to be gamma dose dependent. The sensing properties were identified by measuring the changes of conductivity of film using I-V measurement. Upon exposure to E. coli, the radiated ZnO-rGO films (1.00 vol% GO) exhibited higher sensitivity, as much as 4.62 × 10−3, than un-radiated films, 1.04 × 10−3. This enhancement of the I-V response was attributed to a positive influence of the gamma radiation in these films. The results prove that our ZnO-rGO nanocomposites thin films by gamma radiation demonstrate a strong performance for the detection of microbiological organisms in water.

This study employed Bacillus spp. with α-amylase production isolated from Malaysian hot spring for domestic kitchen food waste treatment contained grains, vegetables, chicken and tuna that mimic the food waste discharge from domestic kitchens in Malaysian household. Results showed that Bacillus licheniformis HULUB1 and Bacillus subtilis SUNGB2 possess excellent amylolytic properties. Highest α-amylase activity was obtained when both isolates were cultivated at pH 6.0 and 65 °C with concentrations of 18.15 U/mL for HULUB1 and 22.14 U/mL for SUNGB2. Stability of α-amylase with significant levels of enzyme activity were recorded at 55–85 °C and pH 5.0–9.0. The extracted mixed α-amylase of HULUB1 and SUNGB2 showed greatest reduction were achieved at day 12 with 45% ± 0.03 solid content at 65 °C. While the mixed culture of HULUB1 and SUNGB2 displayed an enhanced effect on the food waste contents reduction with 43% ± 0.02 solid content at 45 °C after day 12. The findings showed that the combination of the two Bacillus spp. isolates possessed degradation of food wastes at faster rate than α-amylase. It was also pointed out that the standard food waste (SFW) and the treatment process assimilated for this study was suitable for the growth of Bacillus spp., Food Science; Microbiology; α-amylase; Bacillus spp.; Thermophilic; Biodegradation; Food Waste

The use of microalgae as an alternative source of biofuel production has become an emerging topic of interest in recent years. However, the main challenge in the microalgae downstream process lies in the separation of microalgae from the growth media (harvesting process). This study proposed the use of different organic flocculants, namely, cationic guar gum, gum arabic and okra gum, to harvest the microalga Aurantiochytrium sp. SW1 for subsequent extraction of docosahexaenoic acid-rich oil from the microalgae. The physicochemical properties and bioactivities of the cell and extracted oil were studied. The results showed that cationic guar gum at 0.5% w/v and gum arabic at 0.1% w/v were the optimum concentrations for cell harvesting. The highest cell recovery was achieved using cationic guar gum with up to 12.8 g/L culture, which was 3.8-fold higher than that of the control method, probably due to the cationic charge of the cationic guar gum, which exhibited a greater efficiency in coagulating the negatively charged surface of microalgae. Overall, the different flocculants used during harvesting affect the extraction efficiency of lipids and other phytochemicals in the cells. Cationic guar gum significantly produced the highest (p ≤ 0.05) oil yield extracted from the culture, which was up to 25.06% w/w biomass. Interestingly, the significantly highest (p ≤ 0.05) total phenolic content (0.23 ± 0.01 mg gallic acid equivalent/mL) and carotene content (1.67 ± 0.42 mg/mL) were observed in microalgae oil flocculated with okra gum, signifying that the type of flocculant affected the determination of phytochemical content of the extracted oil. The oil obtained from okra gum flocculant also exhibited the highest 2,2-diphenyl-1-picrylhydrazyl scavenging activity (0.89 ± 0.01 mg Trolox equivalent/mL) and ferric reducing antioxidant powder (26.77 ± 1.52 mg Trolox equivalent/mL), which was attributed to the higher concentrations of phenolic compounds and carotene content. This work reveals the potential usage of okra gum as a flocculant with enhanced phytochemical contents and bioactivities.

Hydrogen generation was studied using palm oil mill effluent (POME) as an agro-industrial waste obtained from the palm oil industry. POME was subjected to a dilute acid hydrolysis step by HCl (37% v/v) to release fermentable sugars from cellulosic content. POME hydrolysate obtained was used as a substrate for hydrogen generation. The composition of POME hydrolysate showed glucose and xylose were the main monomeric sugars liberated. Hydrogen production was performed in dark fermentation process, in which the new bacterial strain Clostridium acetobutylicum YM1 was cultivated on POME hydrolysate based on a central composite design (CCD). CCD was constructed by considering three pivotal process variables including incubation temperature, initial pH of culture medium and microbial inoculum size. An empirical model, namely second-order polynomial regression model was generated and adjusted to CCD data. The analysis of empirical model generated showed that the linear and quadratic terms of temperature had a highly significant effect on hydrogen generation (P < 0.01). Furthermore, the quadratic effects of initial pH value of culture medium and inoculum size had a significant effect on hydrogen production at 95% probability level (P < 0.05). The regression model also showed that the interaction effect between temperature and initial pH value of the culture medium on the hydrogen generation was highly significant (P < 0.01). The empirical model suggested that the optimum conditions for hydrogen production were an incubation temperature of 38 °C, initial pH value of 5.85 and inoculum size of 17.61% with predicting the production of a cumulative hydrogen volume of 334.2 ml under optimum conditions. In order to validate the optimum conditions determined, C. acetobutylicum YM1 was cultivated on POME hydrolysate in optimum conditions. Verification test results showed that a cumulative hydrogen volume of 333.5 ml and a hydrogen yield of 108.35 ml H2/g total reducing sugars consumed were produced.

Characterization and production of biosurfactant by a novel bacterial strain isolated from an Iranian oil field was investigated. Biosurfactant has wide applications in oil recovery. A number of ten strains of Bacillus sp. were isolated from oil-contaminated soil samples to study biosurfactant production. Among strains studied, the strain 2IR was selected as a potent biosurfactant-producing bacterium. The identification of the strain 2IR was carried out using scanning electron microscopy, biochemical tests and partial 16S rRNA gene sequencing with generating a phylogenetic tree. Accordingly, the new strain was identified as Bacillus pumilus 2IR. The biosurfactant produced by the strain 2IR was characterized by high performance liquid chromatography, fourier transform infrared spectroscopy and proton nuclear magnetic resonance test. The tests results characterized the biosurfactant produced as a lipopeptide type. In order to attain the highest surface tension reduction of the lipopeptide biosurfactant, culture medium of the strain 2IR was optimized. Experimental results showed that glucose, crude oil, potassium nitrate and ammonium sulfate were pivotal components of the culture medium for biosurfactant synthesis by B.pumilus 2IR. Similar results revealed that optimum medium compositions were 30.31 g/L glucose, 0.8% (v/v) crude oil, 2.88 g/L potassium nitrate and 2.4 g/L ammonium sulfate. A surface tension value of 30 mN/m was obtained in optimum conditions. This research presents new indigenous strain B. pumilus 2IR for synthesis of biosurfactant usable for possible in situ oil recovery.

Fermentative hydrogen generation was studied using palm kernel cake (PKC) as sustainable cellulosic biomass. PKC was subjected to an acid hydrolysis approach using dilute H2SO4 (7% v/v). PKC hydrolysate obtained was then diluted (70%) and used as a substrate for hydrogen generation. Chemical analysis showed that the main fermentable sugars in diluted PKC hydrolysate were glucose, xylose and mannose with the concentrations of 2.75 g/L, 2.60 g/L and 27.75 g/L, respectively. Hydrogen production was carried out by the cultivation of Clostridium acetobutylicum YM1 on PKC hydrolysate. The effect of incubation temperature, the initial pH of culture medium and microbial inoculum size on hydrogen production was studied using a statistical model. The analysis of the model generated showed that the initial pH value of the culture medium and inoculum size had significant effects on the hydrogen production. The study showed that the optimum conditions for the biohydrogen production were 30.57 °C temperature, pH 5.5 and 20% inoculum size. A verification experiment was performed in the optimum conditions determined. Experimental results of the verification test showed that a cumulative hydrogen volume of 1575 ml/L was generated with consuming 2.75 g/L glucose, 2.20 g/L xylose and 16.31 g/L mannose.

Microbial electrolysis cell (MEC) is a potentially attractive green technology to tackle the global warming and energy crisis, which employs electrochemically active bacteria to convert organic matter into hydrogen or a wide range of chemicals, such as methane, acetate, hydrogen peroxide, ethanol, and formic acid, without causing environmental pollution. Until now, probably the cleanest and the most efficient method of producing hydrogen has been MEC. However, this technology is still in its infancy period and poses various challenges towards up-scaling and widespread applications, such as such as lower hydrogen production rate (HPR), high internal resistance, complicated architecture, and expensive materials. New advances are needed in biofilm engineering, materials for electrodes and reactor configuration for successful real-world application of this technology. Thus, the present review deals with development of practical MEC technology and includes the following sections: firstly a general introduction to MECs; their operating principles, thermodynamics of MEC, and energy or voltage losses in the MEC system were provided. Followed by a section on the critical factors affecting MEC performance; microorganisms, anode, cathode, membrane or separator, fuel sources, the state-of-art MECs designs, other key operational factors, and its potential application in microbial production of value added products are discussed in detail. Afterwards, current challenges involved in developing practical MEC systems are highlighted, and outlooks for future development are also suggested. The review aims to assist researcher and engineers to gain fundamental understandings of MEC, and it also provides several future research directions and a road map on how to overcome the barriers, so the MEC technology can be further advanced and applied in larger scale.

Conducting polymers are excellent host materials for nanoparticles of metals and semiconductors. PANI-Ag-Co nanocomposite was prepared by chemical oxidative polymerization of aniline monomer in the presence of nitric acid. PANI-Ag-Co thin films were deposited on the glass substrate using spin-coating technique. The films were characterized by UV-Vis spectroscopy, XRD, AFM and TEM to analyze the internal structure and surface morphology. The performance of the sensor was conducted using I–V measurement to obtain the changes in the current before and after the incubation with E. coli bacteria in water. In UV-visible absorbance bands, a single peak appears at 421.6 nm in each band indicating the Ag-Co alloy nanoparticles were formed. The peaks in the XRD patterns show the crystals are oriented along (111) planes for Ag while (200) plane for Co. AFM images indicate the surface roughness of the PANI-Ag-Co films decreases when the concentration of Co increased. TEM image shows spherical shaped of Ag-Co alloy particles with diameter in the range of 6 – 10 nm. I–V measurements show that the current change of the films increased when incubated in E. coli. The sensitivity on E. coli increases as we increase the Co concentration. PANI-Ag-Co nanocomposite thin films can be explored further for microbial sensor application in future study.