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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 food wastage problem and its associated issues have become a significant threat to sustainable development, particularly in developing countries. Cooked rice, which has been reported to be one of the most abundant regional food wastes, is a substantial feedstock for biofuel production due to its rich carbon content. In this study, both solid-state and acetone–butanol–ethanol (ABE) fermentations were conducted in series with Aspergillus oryzae and aero-tolerant Clostridium acetobutylicum YM1 for the biobutanol production. To validate the process parameters for an industrial-scale process, it is critical to examine the effects of process parameters using a process simulation tool. To this end, by adapting lab-scale process results, a techno-economic evaluation of the biobutanol production from the cooked rice by two-step fermentation was performed using SuperPro Designer®. This study aims to examine various scenarios for cooked rice utilization to produce butanol while examining process optimization and minimization of operational expenses for the aerobic ABE fermentation and microbial saccharification. According to the simulation results, butanol production cost was estimated to be 1.24 $ kg−1, incorporating a cost reduction of 0.58 $ kg−1 from heat integration, steam and power generation, while eliminating costs for the unnecessary commercial enzymes and N2 gas for purging. Finally, sensitivity analysis was applied to demonstrate the plant feasibility concerning potential fluctuations in the changing biofuel market and environmental conditions.

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.

Biosurfactants or microbial surfactants are structurally diverse and contribute to reducing surface and interfacial tension. Apart from being isolated from municipal waste and oil contaminated soil...

Microbial electrolysis cell (MEC) is a promising technology for simultaneous wastewater treatment and bioenergy generation (H2). The mixture of organic compounds present in wastewater acts as the source of free electron in the MECs. H2 production rate and yield by conventional methods including dark fermentation, photo-fermentation and biophotolysis are reported to be lower due to thermodynamic barrier. This thermodynamic barrier can be overcome by applying a small input of electrical energy in an MEC. MECs are not only capable of producing H2 production from wastewater, but it could also be utilized to recover value-added biochemicals or fuels from wastewater via the various integrated process. The present chapter reviews the current applications of MECs in H2 production, wastewater treatment and other value added chemical production along with the advantages of MECs over conventional technologies.

Currently, the harmful gas emission, rapid climate change, air and water pollution, and deterioration of earth's land surface are mainly produced by the aggressive utilization of petroleum-based plastic and the unmanaged garbage disposal including dumping and burning of polymeric products and substances. Many experts from throughout the globe revealed that the dumping of petroleum-based plastic and undecomposed materials is the main principle problem of environmental pollution. Hence, in order to overcome these challenging issues, biopolymers, such as starch, cellulosic-based polymer, and other biodegradable materials, are considered the most promising materials and as alternatives to non-biodegradable petroleum-based materials. This is due to their long shelf life properties such as resistance to enzymatic or chemical reaction and as they are biodegradable in nature. Starch is an abundantly available, highly biodegradable, cheap, and renewable biopolymer. However, some studies have found that the properties of starch biopolymer such as mechanical and water barrier are comparatively low than petroleum-based plastic. Therefore, nanofillers such as nanocellulose are introduced in order to overcome this issue. Nanocellulose has attracted huge attention due to its good physical and mechanical behaviors. In recent years, nanocellulose has also attracted the interest among researchers, since the technology capable to cater the environmental issues. This chapter explains the outline of current development in this particular field, including the isolation, characterization, behaviors, and various applications of nanocellulose reinforced starch biopolymer nanocomposites. Followed by explaining the distinctive properties of nanocellulose and its numerous preparation methods, an arranged introduction of various sources of nanocellulose reinforced biodegradable starch polymers is provided. Herein, nanocellulose reinforced starch biopolymer for engineering and interdisciplinary applications, comprising approaches for the transformation of various sources of cellulose to nanocellulose, and the technique of fabrication for their composites have been studied. Furthermore, the results of nanocellulose on the behavior of starch biopolymers are presented. Finally, the chapter summarizes with a new finding and innovation researches on nanocellulose reinforced starch biopolymer composites. In certain circumstances, an evaluation study was conducted between cellulose nanofiber and cellulose nanocrystals reinforced starch biodegradable polymers. Considering the vast amount of research on nanocellulose reinforced starch biopolymer composites, special highlights on such composites are allowed at the end of the review.

In Asia, uneaten cooked rice is the highest portion amongst many forms of food wastes that are thrown away. In order to make use of the thrown-away rice and potentially use it for liquid fuels, steamed Japanese rice was evaluated on biobutanol production through a two-step fermentation by amylase-producingAspergillus oryzae, and solvent-producingClostridium acetobutylicumYM1. The effects of sterilization and providing anaerobic conditions on solvent production in acetone-butanol-ethanol (ABE) fermentation cannot be underestimated. Several conditions, including aerobic, anaerobic, sterile, and non-sterile were investigated concerning the solvent production capability ofClostridium acetobutylicumYM1. The maximum solvent production was 11.02 +/- 0.22 g/l butanol and 18.03 +/- 0.34 g/l total ABE from 75 g/l dried rice. The results confirmed that the solvent production performance of the YM1 strain was not affected by the sterilization conditions. In particular, 10.91 +/- 0.16 g/l butanol and 16.68 +/- 0.22 g/l ABE were produced under non-sterile and aerobic conditions, which can reduce industrial-scale production costs.

The use of polylactic acid (PLA) and polyhydroxyalkanoates (PHA) polymers in various advanced applications have been certified long time ago due to their promising properties. Processing methods of biodegradable thermoplastic polymer are similar to conventional thermoplastics but required adjustment on processing parameters or incorporations of compatibilizers. The differences in term of viscosity, melt flow rate, and melt strength have caused the existing processing parameters unsuitable for biopolymers. Thermal degradation is the normal issue needed to deal with, during biopolymer processing. Several important process methods, such as extrusion, injection molding, blowing molding, thermoforming, and 3D printing, have been discussed in this chapter for PHA and PLA biopolymers. Besides this, the developmental application of the biopolymers, especially in medical sector, has been reviewed in the last section of this chapter.

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.

Microbial electrolysis cells (MECs) are perceived as a potential and promising innovative biotechnological tool that can convert carbon-rich waste biomass or wastewater into hydrogen (H2) or other value-added chemicals. Undesired methane (CH4) producing H2 sinks, including methanogens, is a serious challenge faced by MECs to achieve high-rate H2 production. Methanogens can consume H2 to produce CH4 in MECs, which has led to a drop of H2 production efficiency, H2 production rate (HPR) and also a low percentage of H2 in the produced biogas. Organized inference related to the interactions of microbes and potential processes has assisted in understanding approaches and concepts for inhibiting the growth of methanogens and profitable scale up design. Thus, here in we review the current developments and also the improvements constituted for the reduction of microbial H2 losses to methanogens. Firstly, the greatest challenge in achieving practical applications of MECs; undesirable microorganisms (methanogens) growth and various studied techniques for eliminating and reducing methanogens activities in MECs were discussed. Additionally, this extensive review also considers prospects for stimulating future research that could help to achieve more information and would provide the focus and path towards MECs as well as their possibilities for simultaneously generating H2 and waste remediation.

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).

The viability of fermentation process is very much depends on the use of a cheap carbon source from lignocellulosic materials. It needs to hydrolyse into simple and readily metabolize carbohydrate using cellulase enzyme. Pycnoporus sanguineus has been able to produce cellulase enzyme with high enzyme activity that can convert lignocellulosic materials into fermentable sugar. P. sanguineus was culture using α-cellulose as carbon source for enzyme production via submerged fermentation (SMF) at different agitation speeds (100 and 150 rpm). Crude cellulase enzyme extracted from fermentation broth by centrifugation was used in hydrolysis of sawdust and sugarcane bagasse at different substrate concentrations (1-5% w/v). It was found that crude cellulase enzyme contain three main enzymes components i.e. endoglucanase, exoglucanase and xylanase with maximum activity of 1.55, 0.45 and 8.0 U/mL respectively that achieved after four days of cultivation at agitation speed of 150 rpm. The most suitable temperature and substrate concentration for sawdust and sugarcane bagasse hydrolysis by cellulase from P. sanguineus was at 30°C and 5% (w/v) where sugarcane bagasse produced maximum of 59.10 g/L fermentable sugar as compared to from sawdust (58.84 g/L). Fermentable sugar productivity was the highest (2.45 g/L/h) when sawdust was use compared to 0.50 g/L/h for sugarcane bagasse. Fermentable sugar produced from agrowastes using cellulase enzymes of P. sanguineus has highest potential as a feedstock for biofuels and biochemicals production.

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.

Butanol was produced from pretreated deoiled rice bran (DRB) in a batch culture of Clostridium acetobutylicum YM1. The DRB was pretreated by acetyl chloride to produce fermentable sugars prior to butanol fermentation. Pretreatment of DRB using 1% acetyl chloride (AC-DRB) resulted in sufficient fermentable sugars (30.88 g/L), which was comparable to that produced by using 1% sulfuric acid (33.5 g/L). Pretreated AC-DRB contained 18.08 g/L glucose, 9.95 g/L xylose, and 2.86 g/L cellobiose. Detoxification of AC-DRB was performed to remove the fermentation inhibitors, such as furfural, 5-hydroxymethyl furfural (HMF), acetic acid, formic acid, and levulinic acid with the removal efficiencies of 92.98%, 98.82%, 51.53%, 38.72%, and 96.21%, respectively, using charcoal. The detoxification with charcoal was more efficient compared to that with XAD-4 resin. Acetone-butanol-ethanol (ABE) fermentation of detoxified AC-DRB (with 1% AC) by XAD-4 produced 5.64 g/L butanol, while detoxification with charcoal of AC-DRB (with 1% AC) produced 6.48 g/L butanol. In detoxified AC-DRB with charcoal, the maximum butanol and ABE yield of 6.48 g/L and 11.82 g/L, respectively, were achieved. This study is the first reported treatment of biomass using acetyl chloride, which was used as a pretreatment method for successful butanol production.

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.

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.

A new solvent-producing Clostridium has been isolated from soil used in intensive rice cultivation. The 16S rRNA analysis of the isolate indicates that it is closely related to Clostridium acetobutylicum, with a sequence identity of 96%. The new isolate, named C. acetobutylicum YM1, produces biobutanol from multiple carbon sources, including glucose, fructose, xylose, arabinose, glycerol, lactose, cellobiose, mannitol, maltose, galactose, sucrose and mannose. This isolate can also utilize polysaccharides such as starch and carboxylmethyl cellulose (CMC) for the production of biobutanol. The ability of isolate YM1 to produce biobutanol from agro-industrial wastes was also evaluated for rice bran, de-oiled rice bran, palm oil mill effluent and palm kernel cake. The highest concentration of biobutanol (7.27 g/L) was obtained from the fermentation medium containing 2% (w/v) fructose, with a total acetone–butanol–ethanol (ABE) concentration of 10.23 g/L. The ability of isolate YM1 to produce biobutanol from various carbon sources and agro-wastes indicates the promise of the use of this isolate for the production of biobutanol, a renewable energy resource, from readily available renewable feedstocks.

In this work, hydrolysis of cellulose and hemicellulose content of palm kernel cake (PKC) by different types of hydrolytic enzymes was studied to evaluate monomeric sugars released for production of biobutanol by Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564) in acetone-butanol-ethanol (ABE) fermentation. Experimental results revealed that when PKC was hydrolyzed by mixed β-glucosidase, cellulase and mannanase, a total simple sugars of 87.81±4.78 g/L were produced, which resulted in 3.75±0.18 g/L butanol and 6.44±0.43 g/L ABE at 168 h fermentation. In order to increase saccharolytic efficiency of enzymatic treatment, PKC was pretreated by liquid hot water before performing enzymatic hydrolysis. Test results showed that total reducing sugars were enhanced to 97.81±1.29 g/L with elevated production of butanol and ABE up to 4.15±1.18 and 7.12±2.06 g/L, respectively which represented an A:B:E ratio of 7:11:1.

This research aimed to study the fermentative production of hydrogen using de-oiled rice bran (DRB) as renewable biomass. DRB was obtained by the extraction of oil content of rice bran samples. DRB was then hydrolyzed by dilute H2SO4 (1% v/v) to obtain DRB hydrolyzate as substrate for hydrogen generation. The composition of DRB hydrolyzate showed that glucose and xylose formed the main fermentable sugars released from acid hydrolysis of DRB. Hydrogen production was performed by the cultivation of new strain Clostridium acetobutylicum YM1 on DRB hydrolyzate in an anaerobic fermentation process. The effect of pivotal operating variables (incubation temperature, initial pH of culture medium and microbial inoculum amount) on hydrogen production was studied using response surface methodology. A second-order polynomial regression model was generated to evaluate hydrogen generation trend under conditions tested. The model analysis revealed the high significance of linear effects of incubation temperature (P < 0.01) and inoculum amount (P < 0.05) on hydrogen generation. The process model also showed that the quadratic effects of the incubation temperature and pH value were significant at 99% probability level and 95% probability level, respectively. Similar results indicated that the interaction effect between incubation temperature and inoculum amount was highly significant (P < 0.01). The regression model suggested that the optimum conditions were an incubation temperature, pH value and inoculum amount of 35.2 °C, 5.5 and 11.6% (v/v), respectively. In order to validate the optimum conditions determined by the model, Clostridium acetobutylicum YM1 was cultivated on DRB hydrolyzates under optimum conditions determined. Verification experiment showed that a cumulative hydrogen volume of 572.5 ml and a hydrogen yield of 132.2 ml H2/g total sugars consumed were generated.

In this study, optimization of growth, lipid and DHA production of Aurantiochytrium SW1 was carried out using response surface methodology (RSM) in optimizing initial fructose concentration, agitation speed and monosodium glutamate (MSG) concentration. Central composite design was applied as the experimental design and analysis of variance (ANOVA) was used to analyze the data. ANOVA analysis revealed that the process which adequately represented by quadratic model was significant (p

Continuous fermentation of dilute acid-pretreated de-oiled rice bran (DRB) to butanol by the Clostridium acetobutylicum YM1 strain was investigated. Pretreatment of DRB with dilute sulfuric acid (1%) resulted in the production of 42.12 g/L total sugars, including 25.57 g/L glucose, 15.1 g/L xylose and 1.46 g/L cellobiose. Pretreated-DRB (SADRB) was used as a fermentation medium at various dilution rates, and a dilution rate of 0.02 h−1 was optimal for solvent production, in which 11.18 g/L of total solvent was produced (acetone 4.37 g/L, butanol 5.89 g/L and ethanol 0.92 g/L). Detoxification of SADRB with activated charcoal resulted in the high removal of fermentation inhibitory compounds. Fermentation of detoxified-SADRB in continuous fermentation with a dilution rate of 0.02 h−1 achieved higher concentrations of solvent (12.42 g/L) and butanol (6.87 g/L), respectively, with a solvent productivity of 0.248 g/L.h. This study showed that the solvent concentration and productivity in continuous fermentation from SADRB was higher than that obtained from batch culture fermentation. This study also provides an economic assessment for butanol production in continuous fermentation process from DRB to validate the commercial viability of this process.

Thraustochytrids are a group of marine fungus-like microheterotrophs of which some can accumulate considerable amounts of the high valued omega-3 oil, docosahexaenoic acid (DHA). In this study, a local thraustochytrid isolate, Aurantiochytrium sp. SW1, was cultivated in a medium containing fructose as the major carbon source. The effects of this carbon source in interaction with yeast extract, monosodium glutamate (MSG) and sea salt were studied using a software-based two level full factorial design. Results showed that fructose as a single factor, has significant positive effect on the volumetric DHA content of SW1. Similarly, its interaction with yeast extract has profound positive effect. However, interactions of fructose with MSG and sea salt were significant negative effects. These results indicate that manipulation of the concentration of fructose in the culture medium may serve as a simple and useful strategy to help achieve preferred amount of DHA.Thraustochytrids are a group of marine fungus-like microheterotrophs of which some can accumulate considerable amounts of the high valued omega-3 oil, docosahexaenoic acid (DHA). In this study, a local thraustochytrid isolate, Aurantiochytrium sp. SW1, was cultivated in a medium containing fructose as the major carbon source. The effects of this carbon source in interaction with yeast extract, monosodium glutamate (MSG) and sea salt were studied using a software-based two level full factorial design. Results showed that fructose as a single factor, has significant positive effect on the volumetric DHA content of SW1. Similarly, its interaction with yeast extract has profound positive effect. However, interactions of fructose with MSG and sea salt were significant negative effects. These results indicate that manipulation of the concentration of fructose in the culture medium may serve as a simple and useful strategy to help achieve preferred amount of DHA.

Optimization of fermentation medium for the production of docosahexaenoic acid (DHA) by Aurantiochytrium sp. SW1 was carried out. In this study, levels of fructose, monosodium glutamate (MSG) and sea salt were optimized for enhanced lipid and DHA production using response surface methodology (RSM). The design contains a total of 20 runs with 6 central points replication. Cultivation was carried out in 500 mL flasks containing 100 mL nitrogen limited medium at 30°C for 96h. Sequential model sum of squares (SS) revealed that the system was adequately represented by a quadratic model (p

Improvement in the butanol production selectivity or enhanced butanol:acetone ratio (B:A) is desirable in acetone-butanol-ethanol (ABE) fermentation by Clostridium strains. In this study, artificial electron carriers were added to the fermentation medium of a new isolate of Clostridium acetobutylicum YM1 in order to improve the butanol yield and B:A ratio. The results revealed that medium supplementation with electron carriers changed the metabolism flux of electron and carbon in ABE fermentation by YM1. A decrease in acetone production, which subsequently improved the B:A ratio, was observed. Further improvement in the butanol production and B:A ratios were obtained when the fermentation medium was supplemented with butyric acid. The maximum butanol production (18.20 ± 1.38 g/L) was gained when a combination of methyl red and butyric acid was added. Although the addition of benzyl viologen (0.1 mM) and butyric acid resulted in high a B:A ratio of 16:1 (800% increment compared with the conventional 2:1 ratio), the addition of benzyl viologen to the culture after 4 h resulted in the production of 18.05 g/L butanol. Manipulating the metabolic flux to butanol through the addition of electron carriers could become an alternative strategy to achieve higher butanol productivity and improve the B:A ratio.

Microbial electrolysis cells (MECs) are generally regarded as a promising future technology for manufacturing green hydrogen from organic material present in wastewaters and other renewable energy sources. However, the development of inexpensive and high-efficient cathode catalyst is the most critical challenge for MECs to become a commercialized H2 production technology. In this study, a non-noble metal electroformed Ni mesh cathode alternatives to typical cathode material (Pt/CC) was intensively examined in a single-chamber membrane-free MEC. To the best of our knowledge, the use of electroformed Ni mesh as the MEC cathode catalyst has not been reported so far. The MEC was operated in fed-batch mode and the performance of the Ni mesh cathode was compared with that of Pt/CC cathode in terms of columbic efficiencies (75 ± 4% vs. 72.7 ± 1%), overall hydrogen recovery (89.3 ± 4% vs. 90.9 ± 3%), overall energy efficiency (62.9 ± 5% vs. 69.1 ± 2%), the maximum volumetric hydrogen production rate (4.18 ± 1 m3 H2/m3 d vs. 4.25 ± 1 m3 H2/m3 d), volumetric current density (312 ± 9 A/m3 vs. 314 ± 5 A/m3). The obtained results in this study highlight the great potential of using the electroformed Ni mesh catalysts as a viable cathode material for hydrogen production in MECs.

MEC (Microbial electrolysis cell) is an emerging and promising bio-electrochemical process for sustainable production of hydrogen gas. The performance and cost of cathode materials are the most important factors in MEC. In order to enhance MEC performance and reduce the fabrication and operational costs of electrodes, a wide range of cathode materials have been developed and tested in the recent years. However, no standard and systematic analytical method has been developed to make a comparative assessment of the cathode materials in MECs. In this study, a statistical method, namely GRA (grey relational analysis) was exploited to evaluate hydrogen evolution performance of eight different non-precious metal alloy cathodes, including stainless steel alloys 304, 316, 420, A286, and nickel alloys 201, 400, 625 with Ni HX in comparison to precious metal of Pt (platinum). Statistical results revealed that materials tested were ranked based on the grey relational grade values as ASS 286 > Pt > SS 304 > Ni 625 > SS 420 > Ni HX > Ni 400 > Ni 201 > SS 316. The results obtained showed stainless steel A286 had the best efficiency in MEC test based on grey relational grade. This study indicated that GRA could be used as a novel method to assess the performance of cathodes in MEC.

A newly isolated strain of Clostridium acetobutylicum YM1 has a unique property of producing biobutanol from glucose under aerobic conditions. This strain exhibited the capability to grow and produce high concentrations of biobutanol under different concentrations of dissolved oxygen (DO). The growth profile and solvent production in a 5 L bioreactor were similar under anaerobic and aerobic conditions (100% initial DO saturation), and the final biobutanol production was 12.18 and 12.30 g/L, respectively. The addition of reducing chemical agents, without creating anaerobic conditions, to the culture of YM1 enhanced the production of biobutanol. Strain YM1 possesses different enzymes that are responsible for oxygen scavenging, such as superoxide dismutase (SOD), catalase and NADH/NADPH oxidases. This study provides a simple operation strategy for more efficient biobutanol production by using an aerotolerant strain of C. acetobutylicum YM1 without the need to flush the medium with nitrogen gas to ensure anaerobic conditions.

Repeated batch culture of Cunninghamella bainieri 2A1 was performed to investigate mycelial pellet formation in fungal lipid production process. Experimental studies were performed based on the size and structural morphology of pellets formed with consideration of harvesting times and harvested volumes of repeated batch culture. Electron microscope images showed that fungal cells formed mycelial pellets with varied size from 575 µm × 586 µm in 60 % harvesting volume with a hairy loose morphology to 1.01 mm × 1.18 mm in 90 % harvesting volume with a tightly packed dense morphology.

Thraustochytrids are marine protists belonging to the class Labyrinthula of the kingdom Chromista. This group of microbes is considered a promising alternative source of high-valued omega-3 oils, especially docosahexaenoic acid (DHA, C22:6 n 3), replacing fish oil which is the current major source of DHA and eicosapentaenoic acid (EPA, C20:5 n 3). Our new isolate, SW1, was considered to be an Aurantiochytrium based on its morphology, fatty acid profile and molecular phylogenetic analysis. Microscopic observations revealed that SW1 has high similarity to Aurantiochytrium limacinum ATCC MYA-1381 (SR21), possessing spherical vegetative cells which undergo repeated bipartition to form diads, tetrads, octads and zoosporangia that release motile zoospores. When cultivated in four different media, SW1 produced the highest biomass (13.17 g/L) and DHA (3.6 g/L) in a medium composed of glucose, sea salt, monosodium glutamate (MSG) and yeast extract. Visualization of lipid droplet development in SW1 using Sudan Black B dye revealed that lipid droplets enlarge to occupy almost the entire cell volume within 72 to 96 h of cultivation. This strain was also found to be able to utilize various saccharides as carbon source. The results of this study show that Aurantiochytrium sp. SW1 is a potential candidate to be developed as commercial microbial DHA producer.

Palm oil mill effluent (POME), an abundant and low-cost agro-industrial residue, was utilized for the production of butanol in the anaerobic process of acetone–butanol–ethanol (ABE) fermentation. The ABE process was performed by the cultivation of Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564) in raw POME medium without supplementation. The effect of various process parameters, including pH, incubation temperature, agitation and inoculums size on butanol production, was studied. Experimental results showed that the highest butanol levels could be produced when the initial pH of culture medium, incubation temperature, agitation speed and inoculums size were set at 5.8, 30 °C, 100 rpm and 15% (v/v), respectively. Results revealed that the existence of crude palm oil (CPO) in the POME composition had an adverse effect on butanol synthesis by Clostridial cells. The highest butanol and ABE concentrations of 0.9 g/L and 2.09 g/L were produced, respectively, when operating variables tested were set at their optimum levels under the absence of CPO.