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In our current work, we have optimized six physicochemical parameters (light intensity, light period, pH, inoculum size, culture period, and salt concentration) toward growth and chlorophyll synthesis using isolated fresh water microalgae Chlorella thermophila [contains ∼6% (w/w on dry biomass basis) chlorophyll]. Here, both experimental and computational [Taguchi orthogonal array (TOA), artificial neural network (ANN), and genetic algorithm (GA)] approaches were employed for the process intensification. Results revealed that the content of biomass and chlorophyll were enhanced by 118% and 95%, respectively, with productivity enhancement of 30% for biomass and 61% for chlorophyll from the optimization of physicochemical parameters. Further, optimum light intensity was found to be 128 µmol m−2 s−1 after conducting experiments in optimized chemical and physicochemical conditions, contributing to the enhancement of productivity of 46% for biomass and 106% for chlorophyll. Urea was found to be the most effective nitrogen source with an increase of 70% and 160% biomass and chlorophyll productivity, respectively. Moreover, sucrose as a carbon source contributed to an increase of 97% and 264% biomass and chlorophyll productivity.

Optimum light exposure for the cultivation of microalgae to obtain high biomass density varies between different species. In the current work, isolated microalgae strain Chlorella thermophila was used to investigate the growth and biomolecular content under exposure of various light regimes in a pilot-scale flat plate photobioreactor (50 L). Here, three different lighting patterns namely fixed (4500 lx intensity with 14:10 light/dark ratio), variable (0−4500 lux variable intensity with 14:10 light/dark ratio) and continuous mode (4500 lx intensity with 24:0 light/dark ratio) were studied for the evaluation of the importance of light/dark period and sinusoidal illumination. Results demonstrated that the light/dark period had a significant influence on the growth and synthesis of biomolecules. The biomass concentration at fixed mode was found to be 5.6 and 1.9 fold higher compared to continuous mode and variable mode, respectively. Chlorophyll content was found to be the highest (4.8 %, w/w) in fixed mode while protein content was highest (68 %, w/w) in variable mode. The highest content of carotenoids (0.69 %, w/w) and carbohydrates (38 %, w/w) were noticed in continuous lighting mode. The highest average productivity of 16.4, 10.5, 4.03, 0.76, 0.6 (mg/L.day) were achieved for biomass, proteins, carbohydrate, chlorophylls and carotenoids, respectively in fixed mode.

Chlorophylls and carotenoids can be extracted from microalgae using various solvents. However, there is lack of studies regarding the comparison of extraction yield of these pigments from wet and dry microalgal biomass using different combination of cell disruption methods. Therefore, in this work, we have investigated the comparison of the extraction yield of chlorophylls and carotenoids from the wet and heat-dried microalgal biomass (isolated Chlorella thermophila) using ethanol. Extraction parameters such as homogenisation time, homogenisation speed, solvent temperature, solid-solvent ratio, boiling time and microwave time have been optimised. Chlorophyll extraction yield was observed to be 2.7 fold higher from wet biomass than dry biomass while carotenoid yield was 6.7 fold higher. Highest chlorophyll yield (∼60 mg/g-dry biomass) was observed at 6 min of homogenisation time, 10,000 rpm, solid solvent ratio of 1 mg/mL and 58 °C of solvent temperature from wet biomass with extraction efficiency of ∼94 %. Highest carotenoid yield was noticed following the same conditions of chlorophyll extraction except 4 °C of solvent temperature. The modelling of the extraction process was performed using artificial neural network (ANN) which may be useful for the scale-up of the extraction process at the industrial level.

The production of multiple products from microalgae is essential for economic sustainability and the knowledge of optimum cultivation conditions for high growth and biomolecule synthesis of a microalgal strain is the prerequisite for its commercial production. In this work, optimization of nutrient concentrations for the cultivation of isolated

Microbial short and long-chain hydrocarbons can be employed to produce high-quality vehicular fuels that can reduce greenhouse gas emission. Here, we describe the vital microorganisms and their metabolic pathways involved in the biosynthesis of hydrocarbon biofuels. This chapter's primary focus is to provide detailed information about how metabolic engineering can enhance the production of hydrocarbons based on the recently published literature. We also discussed the challenges and possible solutions in the current research efforts to scale-up the microbial production of hydrocarbon biofuels. Despite several hurdles, combined efforts toward designing high hydrocarbon-producing strains, finding cheaper feedstocks, and reducing the toxic stress of hydrocarbons to the strains will help to the build industrial-scale production plants of microbial hydrocarbons.

The production of multiple products from microalgae is essential for economic sustainability and the knowledge of optimum cultivation conditions for high growth and biomolecule synthesis of a microalgal strain is the prerequisite for its commercial production. In this work, optimization of nutrient concentrations for the cultivation of isolated Chlorella thermophila was performed by manipulating nine nutrients with the objectives of maximization of growth, carbohydrate, protein, and chlorophyll contents. Experiments were designed and effects of the parameters were studied using Taguchi orthogonal array (TOA). Experimental results of TOA were used for modeling artificial neural networks (ANN) followed by the optimization using genetic algorithm (GA) to find global optimal solutions. Results showed an increase of 36, 88, 36, and 88% for growth, carbohydrates, proteins, and chlorophylls, respectively, at optimal combinations of parameters given by TOA. Results obtained through the ANN-GA optimization were 9, 10, and 3% more compared to the TOA for biomass, carbohydrates, and chlorophylls, respectively with experimental verification. Nitrates and bicarbonate were found to play the most pivotal role in biomass and biomolecule synthesis of the isolated microalgal strain. Results of the current investigation can be used in the industrial scale-up for the production of multiple products using the biorefinery approach.

Background: :North east region of India is well known as biodiversity hotspot with endemic flora and fauna. Organisms belonging to the cyanobacterial species are commonly known as blue green algae and are found in diverse categories in the environment of north-east India. Potentials of these cyanobacterial species are mostly unexplored. Present study aimed to isolate, identify and evaluate the potential cyanobacterial strains for the sustainable producers of biomolecules with agricultural, therapeutic and industrial significance.Methods::Growth and biochemical characterization were performed with the isolated cyanobacterial species to investigate the growth kinetics, cellular pigments (carotenoid, phycobiliprotein and chlorophyll), protein, carbohydrate and lipid content.Results::Three Phormidium sp., one Oscillatoria sp., and one Microcoleus sp. were isolated from the Tripura state (North-east region of India). Results revealed that isolated Oscillatoria sp. has high lipid (~20%), protein (~40%), and carbohydrate (~30%) yield. Further, two isolated Phormidium sp., produced significant amount of carotenoids (~23 mg/gm dry biomass), phycobiliprotein (~20-25%) and high protein (~55%). Microcoleus sp. produced 62% carbohydrate and 20% phycobiliprotein with significant amount of carotenoids (~17 mg/gm dry biomass).Conclusion::Isolated Oscillatoria sp. is the promising resource for lipid and nutritional supplement due to high accumulated primary metabolites. Two Phormidium sp., can be used as animal and human nutritional food supplement and also can be further investigated for pigment production at industrial scale. Isolated Microcoleus sp. is the potential resource of carbohydrate and pigment. Isolated cyanobacterial strains are identified as viable candidates for the industrial production of biomass as well as other value added biomolecules.

A kinetic model based on Michaelis-Menten assumptions is developed here for enzymatic hydrolysis of cellulose using cellulase enzyme derived from Trichoderma reesei. Further, to assess the inhibition of enzyme and the nature of inhibition by different sugars (glucose, galactose, mannose, xylose and cellobiose) the primary kinetic model is modified with the inhibition kinetics. The enzymatic reaction was carried out at pH = 4.8, temperature = 50 °C, solid loading of 1:20 and at 100 rpm stirrer speed. It was observed among all the sugars, only xylose (five carbon sugars) showed non-competitive inhibition with Ki = 27.2 mM and Vmax = 0.19 g L−1h−1. Glucose and cellobiose manifested competitive inhibition with almost comparable inhibition constants (Ki) of 24.7 and 26.3 mM respectively, while Vmax = 0.26 g L−1h−1. On the contrary, with galactose and mannose, the inhibition constants decrease to 10.9 and 11.1 mM respectively. Statistical analysis shows that cellobiose attributes to a maximum inhibition with 72% reduction in reducing sugar production. On the contrary, the minimum inhibitory effect with 11% reduction in sugar production was observed with xylose. At the end, ANOVA analysis manifests that the effect of different sugars are much significant in inhibiting the enzyme compared to the substrate concentration in case with the cellulase enzyme from Trichoderma reesei.

Numbers of high valued and low volume products from microalgae are already in the market and more number of products is yet to be launched. Downstream processing is the key steps to maintain the quality of the products. Therefore, this review is focused on the downstream processing of the microalgae and cyanobacterial cells for commercial production of biomolecules such as pigments (chlorophyll and carotenoid), protein, carbohydrate (agar, carageenan, alginate, fucoidan) and biopolymers. It also covers the most recent preferred downstream processes for the industries for accomplishing the desired quality of the product and recent important filed patents on downstream processing of microalgae. Further, this article highlights the recent investments made by the industries towards commercial production of microalgal-based biofuels and bio-products worldwide.

In current work, an optimum solid loading (solid: liquid = 1:20), pH (4.8), temperature (50°C), and enzyme dosing of 20 filter paper unit (amount of enzyme required to release 1 µmol of glucose as reducing sugar from filter paper in per mL per minute) were enumerated for enzymatic hydrolysis of banana stem using cellulase from Trichoderma reesei. Further, inhibition study on enzymatic hydrolysis of banana stem was investigated by the supplementation of monosaccharides (glucose, galactose, mannose, xylose, and arabinose), disaccharide (cellobiose), and inhibitors (acetic acid and furfural obtained from pre-enzymatic hydrolysis steps). Glucose and cellobiose showed inhibitory effect on enzymatic hydrolysis of pretreated banana stem at or above 8 g/L while galactose, mannose, and xylose showed a significant inhibitory effect at or above 4 g/L. Instead of inhibition, arabinose enhanced the enzymatic hydrolysis with increase in total reducing sugars. Acetic acid did not show any significant inhibition ...

Depletion in the fossil fuel reserves and the unceasing rise in the greenhouse gas emissions due to excessive use of fossil fuels has become a subject of worldwide concern. Production of microalgal biomass using the carbon dioxide (CO2) laden flue gas is identified as one of the potent solutions to the trap the excessive emissions of CO2 from entering into the atmosphere along with the production of renewable and sustainable biofuel thereby, combating both energy crisis and global warming. Understanding and optimizing the parameters affecting the microalgal growth process is crucial prerequisite for effective CO2 bio-fixation using microalgae in photobioreactors (PBRs). Chlorella sp. BTA 9031 was selected as a potential strain for biomass and lipid production under varying temperatures (20–40 °C), light intensity (30–100 μmol m−2 s−1) and CO2% (4–15%). These three main operating factors were optimized through Central Composite design (CCD) approach of Response Surface Methodology (RSM). The optimal conditions for attaining both maximum biomass and total lipid content were selected to be 28.26 °C, 76.64 μmol m−2 s−1 and 4.00% CO2. Under the optimum conditions, CO2 bio-fixation rate was observed to 0.235 g L−1 d−1 of Chlorella sp. BTA 9031. Confirmatory experiments confirmed that the model predictions were in good agreement with the experimental results.

Asterarcys sp. has been isolated from the forest area of Tripura, India, which is a part of biodiversity hotspot under the north east region of India and remains largely unexplored. In this study, we have identified the isolated algae strain by rRNA sequence analysis. For the first time, ultrastucture morphology with surface elemental analysis of this strain was revealed in this study. In addition, biochemical characterization (e.g. chlorophyll, protein, carbohydrate and lipid) along with growth rate was performed by varying macro nutrient source of carbon, nitrogen and phosphorus under photoautotropic culture condition. Isolated Asterarcys sp. has shown sustainability in wide range of pH. High biomass (0.56 g L −1 ) produced by this strain in nitrogen limited condition (N:P ratio ∼8.7). Variation of macronutrients shows that this strain is enriched with carbohydrate (30–60% of dry biomass) and protein (30–50% of dry biomass) content with low lipid accumulation (6–11% of dry biomass). In a nutshell, Asterarcys sp. BTA 9034 has the potential to be used in industrial application for its high protein and carbohydrate content and with its ability grow in outdoor environmental conditions.

Microalgae are claimed to be the most promising non-food based feedstock for generation of biofuels. However, achieving a high total lipid content with photoautotrophic culture is still challenging. Hence, a viable method to enhance the algal biomass and target product is to observe growth of microalgae under heterotrophic or mixotrophic conditions. In the current study the influence of light and carbon sources under various nutritional modes viz., phototrophic, heterotrophic and mixotrophic to augment the biomass and lipid production of Chlorella sorokiniana BTA 9031 isolated from coalfield was studied. Carbon dioxide (CO2), sodium bicarbonate, sodium acetate, fructose and molasses, an industrial bye-product was used as the carbon sources. The highest biomass concentration of 1.55 g L−1 and total lipid content of 30.6% of dry cell weight (DCW) was obtained when the microalgae was grown using 5 g L−1 of molasses as a carbon source under mixotrophic condition. The initial and final concentration of sugars present in the media supplemented with molasses was determined using high performance liquid chromatography (HPLC). To study the effect of sunlight, microalgae were maintained in outdoor photobioreactors with the respective carbon sources. C12:0, C14:0, C15:0, C18:0, C14:1, C15:1, C17:1, C18:1 and C20:0 fatty acids were identified by fatty acid methyl ester (FAME) analysis. The present work also provides a comparison of biomass concentration and total lipid content obtained during the three culture modes along with the outdoor cultures. Hence, Chlorella sorokiniana BTA 9031 could be considered to be a potent candidate for production of biodiesel by utilizing the cheap carbon source, molasses under mixotrophic condition.

Selection of suitable strain of microalgae is the crucial factor for large-scale production of algae-based products. Efforts have been made here for isolation, identification and biochemical characterization of five microalgae strains collected from Tripura (a small state in north-eastern region of India). Two Chlorococcum sp. (NITAAP008 and NITAAP019) demonstrate their high lipid (15–24%), equal amounts of carbohydrate and protein (35–40%), with specific growth rate of 0.13 day−1. These strains are potential resource for biofuel production. After lipid extraction, remaining biomass can be used as source of carbohydrate for the production of other biofuels. One isolated strain is identified as Chlorella sp. (NITAAP009) and shows 22–33% carbohydrate, 41–50% protein and 5% chlorophyll with specific growth rate of 0.125 day−1. Another Chlorella sp. (NITAAP011) isolated from lake area exhibits significant chlorophyll (5–6.4%), 30–50% carbohydrate, 48–60% protein and low lipid (1–10%) with lower specific growth rate (0.10 day−1). Both strains are having industrial competence for chlorophyll production due to their synthesizing ability of significant amount of chlorophyll (5–6.4%). The last one, Korshikoviella sp. (NITAAP017), has 15–18% lipid, 22–34% carbohydrate, 30–43% protein and 3–4% chlorophyll with specific growth rate of 0.12 day−1 and can be used for food supplement production or lipid synthesis. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

The present study aims towards the investigation of lipid production capability of microalgae isolated from coal mining site. The biomass production and lipid productivity of the isolate was studied under the influence of different bicarbonate, nitrate, and phosphate concentration. The production of biomass was observed to be highest at 8.4, 0.75, and 0.06 gL−1 of bicarbonate, nitrate, and phosphate concentrations. The role of bicarbonate supplementation under different nutritional starvation conditions viz. N+ P+, N– P–, N+ P–, and N– P+ with and without sodium bicarbonate respectively was also evaluated. Addition of sodium bicarbonate increased the lipid content to 35% of dry cell weight (DCW) and carbohydrate content to 52% of DCW under the nitrate and phosphate nutritional starvation conditions. The results revealed that the microalgae grown in sodium bicarbonate can be a promising feedstock for biodiesel production. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1498–1506, 2017

Microalgal biomass is composed of different valuable metabolites that can satisfy the requirements of renewable biofuels, alternative proteins, carbohydrates, and food grade natural colorants. Production of a specific product from microalgae has been proved to be economically infeasible on the commercial scale except for the production of high-value products (e.g. carotenoids and phycobiliproteins). Therefore, the simultaneous extraction of multiple products is essential to bring pragmatism for the production of biofuels, proteins, and carbohydrate derived products from microalgal biomass. In order to obtain multiple products, various strategies have been implemented using potential techniques of cell disruption and biomass fractionation based on the priorities of products. Conventional approaches of downstream processing have often proved to be inefficient in the case of integrated fractionation systems. This is attributable to the divergent nature of the intracellular metabolites of microalgae and their vulnerability toward the different chemicals and conditions of those downstream processes. However, three phase partitioning (TPP), aqueous two-phase separation, membrane separation, supercritical fluid extraction (SFE), and pressurized liquid extraction (PLE) are some of the advanced techniques which have been proved to be useful in this regard. Choice of cell disruption mechanisms is critical for several purposes, such as the selective release of metabolites into a suitable solvent, preservation of bioactivity of molecules and cost-savings. Unfortunately, consolidated report for the fractionation of priority-based products from microalgal biomass using these techniques is lacking. Therefore, in this review, we have critically discussed the different strategies for the priority-based multiple products by implementation of the advanced techniques.

In the present work feasibility of utilizing various carbon sources in enhancing the biomass and lipid productivity of two species Chlorella sp. BTA 9031 and Chlamydomonas sp. BTA 9032 isolated from Indian coalfields was investigated. Carbon dioxide (CO2), sodium acetate, sodium bicarbonate, fructose and two very cheap carbon sources were used namely, cheese whey permeate (CWP) and molasses. The biomass concentration obtained using CWP and molasses were higher than that obtained with refined carbon source, fructose and sodium acetate. Due to the presence of growth promoting factors present in CWP, highest biomass productivity of Chlorella sp. BTA 9031 and Chlamydomonas sp. BTA 9032 were 75 and 43 mg L−1 d−1 respectively. The highest total lipid (38.6%) was obtained in Chlamydomonas sp. BTA 9032 using CWP as a carbon source. In both the microalgal species C13:0, C14:0, C18:0, C14:1, C15:1, C17:1 and C20:0 were identified as the major FAMEs which are suitable to be used as biodiesel components. Hence, CWP could be served as an alternative carbon source for mixotrophic algae cultivation and biodiesel production.

Gradual rise in levels of atmospheric carbon dioxide (CO2) due to burning of fossil fuels has become a matter of environmental concern in the recent years. In this alarming situation capturing CO2 and storing it to restrict its release to the atmosphere could be an attractive approach toward mitigation. Photosynthesis has been recognized as the most sustainable means to arrest CO2 from the atmosphere and microalgae; a photosynthetic microorganism has been identified as the potential sequestering candidate with the highest carbon fixing capabilities. Cyanobacteria and algae have developed their own exclusive editions of photosynthetic carbon concentrating mechanisms (CCMs) to aid ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) in efficient CO2 capture. Carbonic anhydrase (CA), a zinc-containing metallo-enzyme has been observed to play a key role in the CCM by catalysing the reversible hydration of CO2 into bicarbonate and a proton thereby helping in fixation of atmospheric CO2. This review gives an account of the importance of the different types of CA enzymes along with its locations, mechanism of action and the various studies on biosequestration of CO2 through microalgae. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1605–1615, 2016

The scarcity of fossil fuels has urged the economically developed countries to find the resources for an alternative energy sources. In apprehension to this, biofuels, like bioethanol and biobutanol, produced from lignocellulosic biomass were considered as potential alternative. There are several methods for the pretreatment of biomass before it is being used as a feedstock for the production of fermentable sugars. However, one of the crucial concerns here is to enumerate an economic pretreatment scheme that can be implemented in large scale for the production of mostly exposed cellulosic part from biomass. This will ensure an effective hydrolysis of cellulose for the production of fermentable sugars and the production of biobutanol from these derived sugars. Moreover, the keynote understanding of an effective fermentation is the production of less inhibitory compounds like furfural, hydroxymethyl furfural during the hydrolysis of cellulose. Enzymatic hydrolysis of cellulose was reported as the mo...

Microalgae and cyanobacteria are promising sources of biodiesel because of their high oil content (∼10 fold higher) and shorter cultivation time (∼4 fold lesser) than conventional oil producing territorial plants (e.g., soybean, corn and jatropha). These organisms also provide source of several valuable natural chemicals including pigments, food supplements like eicosapentanoic acid [EPA], decosahexaenoic acid [DHA] and vitamins. In addition, many cellular components of these organisms are associated with therapeutic properties like antioxidant, anti-inflammatory, immunostimulating, and antiviral. Isolation and identification of high-yielding strains with the faster growth rate is the key for successful implementation of algal biodiesel (or other products) at a commercial level. A number of research groups in Europe, America, and Australia are thus extensively involved in exploration of novel microalgal strain. Further, genetic engineering provides a tool to engineer the native strain resulting in transgenic strain with higher yields. Despite these efforts, no consensus has yet been reached so far in zeroing on the best microalgal strain for sustainable production of biofuel at reasonable cost. The search for novel microalgal strain and transgenesis of microalgae, are continuing side by side with the hope of commercial scale production of microalgae biofuel in near future. However, no consolidated review report exists which guides to isolate and identify a uncontaminated microalgal strain along with their transgenesis. The present review is focused on: (i) key factors for sample collection, isolation, and identification to obtain a pure microalgal species, (ii) present status for isolation of microalgal strains worldwide based on geographical location and habitat, (iii) the current research for application of genetic engineering tools for enhanced production of biodiesel and value added chemicals, and (iv) the comparison of different cultivation systems for genetically modified strain.

Environmentally hazardous solid waste is renewed to the feedstock of bio-fuel through the recovery of good quality fermentable sugars by acid hydrolysis of the waste newspapers. Conflicting effects of the variables of acid hydrolysis on the yield of fermentable sugars; and that on the generation of undesired inhibitors to subsequent enzymatic hydrolysis for the production of bio-fuel are compared to select the best condition of hydrolysis. The roles of temperature, acid concentration, the ratio of inorganic to organic acids on the yield of desired total sugars (TS) and lignosulfonate (LS), and that on the reduction of inhibitors such as 5-hydroxymethyl furfural (HMF) and acetic acid with time are studied. The hydrolysis experiments are performed at two different temperatures (80 °C and 121 °C), in the acid concentration range of 0.25–1 % (w/v) and with different ratios of two types of acids. The maximum recovery of TS is obtained as 17 % (w/w) at an acid concentration of 1% (w/v), the temperature of 121⁰C at a time of 60 min. Both of HMF and acetic acid are produced only at 121⁰C. The best condition of acid hydrolysis is found as the temperature of 121⁰C, a mixture of sulphuric acid to citric acid of the ratio 3:1 at a hydrolysis time of 60 min for higher values of desired TS and LS with a manageable production of inhibitors. The finer tuning of the hydrolysis variables to produce quality fermentable sugars is promising for the economical production of bio-fuel.

The superiority of biobutanol as a fuel for vehicles over other biofuels has been reported numerous times in recent years (Kumar and Gayen, 2011). Therefore, fermentative production of butanol has attracted the attention of various new research groups in academia and industries. In a review, we have already summarized the development and challenges in fermentative production of biobutanol until 2011 (Kumar and Gayen, 2011). In this chapter, we will highlight the further developments in this field along with the outstanding challenges. In spite of several advantages of butanol as fuel for vehicles, there are still some challenges in acetone-butanol-ethanol (ABE) fermentation in terms of low butanol titer, low productivity, and low yield, high cost of pretreatment of cellulosic feedstocks, presence of toxic compounds in feedstock hydrolysates, product inhibition, and costly and low efficiency recovery processes, which make biobutanol less competitive than other biofuels like bioethanol and biodiesel (Zheng et al., 2015). These challenges are being addressed using several strategies. Details of these strategies are discussed in different sections of this chapter.

Gradual increase in concentration of carbon dioxide (CO2) in the atmosphere due to the various anthropogenic interventions leading to significant alteration in the global carbon cycle has been a subject of worldwide attention and matter of potential research over the last few decades. In these alarming scenario microalgae seems to be an attractive medium for capturing the excess CO2 present in the atmosphere generated from different sources such as power plants, automobiles, volcanic eruption, decomposition of organic matters and forest fires. This captured CO2 through microalgae could be used as potential carbon source to produce lipids for the generation of biofuel for replacing petroleum-derived transport fuel without affecting the supply of food and crops. This comprehensive review strives to provide a systematic account of recent developments in the field of biological carbon capture through microalgae for its utilization towards the generation of biodiesel highlighting the significance of certain key parameters such as selection of efficient strain, microalgal metabolism, cultivation systems (open and closed) and biomass production along with the national and international biodiesel specifications and properties. The potential use of photobioreactors for biodiesel production under the influence of various factors viz., light intensity, pH, time, temperature, CO2 concentration and flow rate has been discussed. The review also provides an economic overview and future outlook on biodiesel production from microalgae.

Clostridium acetobutylicum is a strict anaerobe which exhibits two distinct steps in its metabolic network. In the first step, sugars are oxidized to organic acids (acetic and butyric). This is accompanied with growth. The acids produced in the first phase are re-assimilated into solvents (acetone, butanol, and ethanol) in the second phase of metabolism. The two phases are hence called acidogenesis and solventogenesis, respectively. In this work, using Elementary Mode Analysis (EMA), we quantify fluxes through Elementary Modes under different physical and chemical conditions. Our analysis reveals that, in response to external stresses, the organism invokes Elementary Modes which couple acidogenesis and solventogenesis. This coupling leads to the organism exhibiting characteristics of both, acidogenesis and solventogenesis at the same time. Significantly, this coupling was not invoked during any "unstressed" conditions tested in this study. Overall, our work highlights the flexibility in Clostridium acetobutylicum to modulate its metabolism to enhance chances of survival under harsh conditions.

Hydrogen gas exhibits potential as a sustainable fuel for the future. Therefore, many attempts have been made with the aim of producing high yields of hydrogen gas through renewable biological routes. Engineering of strains to enhance the production of hydrogen gas has been an active area of research for the past 2 decades. This includes overexpression of hydrogen-producing genes (native and heterologous), knockout of competitive pathways, creation of a new productive pathway, and creation of dual systems. Interestingly, genetic mutations in 2 different strains of the same species may not yield similar results. Similarly, 2 different studies on hydrogen productivities may differ largely for the same mutation and on the same species. Consequently, here we analyzed the effect of various genetic modifications on several species, considering a wide range of published data on hydrogen biosynthesis. This article includes a comprehensive metabolic engineering analysis of hydrogen-producing organisms, namely Escherichia coli, Clostridium, and Enterobacter species, and in addition, a short discussion on thermophilic and halophilic organisms. Also, apart from single-culture utilization, dual systems of various organisms and associated developments have been discussed, which are considered potential future targets for economical hydrogen production. Additionally, an indirect contribution towards hydrogen production has been reviewed for associated species.

Present study is a critical analysis and subsequent development of an analytical tool to measure the total sugar concentration in a carbohydrate mixture comprising both hexose and pentose. For this purpose, individual sugars were measured and standardized with anthrone reagent prepared in an ice-cold 98 % sulphuric acid followed by 3 min of boiling. Furthermore, regression analysis was performed after mathematical manipulation with the individual standards to formulate a linear relation between the absorbance of the mixture and its concentration, which satisfies Beer’s law. It was found that the correlation coefficient for the equation is 0.973, when confidence interval was set at 0.95. The validation was done with a synthetic mixture of concentrations at 0.17 and 0.22 g/L (as range was ensured between 0.1 and 0.3 g/L) and also with the carbohydrate mixture as the prehydrolyzate obtained after the pretreatment of banana stem, which showed around 94.1 % accuracy and higher sensitivity with the cellulose present in the mixture. Thus, the method is evident to quantify the total sugars accurately obtained from hydrolyzed lignocellulosic biomass.

Biobutanol can become the replacement of petroleum gasoline in near future. However, economic feasibility of biobutanol production from ABE fermentation is suffering due to the unavailability of cheap feedstocks, production inhibition and inefficient product recovery processes. Here, economic analysis of ABE fermentation has been performed based on cellulosic (bagasse, barley straw, wheat straw, corn stover, and switchgrass) and non-cellulosic (glucose, sugarcane, corn, and sago) feedstocks, which are widely and cheaply available in agriculture based countries. Analysis shows that utilization of glucose required 37% lesser total fixed capital cost than the other cellulosic and non-cellulosic feedstocks for the per year production of 10,000 tonnes of butanol. However, the production cost of butanol from glucose was fourfold higher than sugarcane and cellulosic materials because of its (glucose) high cost. The cost of sago also affected threefold production cost of butanol comparative to other feedstocks. Therefore, these two substrates turned the biobutanol production far from being economically feasible. Interestingly, sugarcane and cellulosic materials showed suitability for economically feasible production of butanol with the production cost range of $0.59–$0.75 per kg butanol. Consequently, quantitative variation in the design and process parameters namely fermentor size, plant capacity, production yield using sugarcane and cellulosic materials as raw materials, trigger significant reduction in unitary cost of butanol up to 53%, 19%, and 31% respectively. Therefore, these parameters will play significant role in making the butanol production economical from cheaper feedstocks (sugarcane and cellulosic materials). Further, high sensitivity of production cost from the product yield postulates significant manipulation in genome of butanol producing bacteria for improving the yield of ABE fermentation.

Corynebacterium glutamicum is commonly used for lysine production. In the last decade, several metabolic engineering approaches have been successfully applied to C. glutamicum. However, only few studies have been focused on the kinetics of growth and lysine production. Here, we present a phenomenological model that captures the growth and lysine production during different phases of fermentation at various initial dextrose concentrations. The model invokes control coefficients to capture the dynamics of lysine and trehalose synthesis. The analysis indicated that maximum lysine productivity can be obtained using 72 g/L of initial dextrose concentration in the media, while growth was optimum at 27 g/L of dextrose concentration. The predictive capability was demonstrated through a two-stage fermentation strategy to enhance the productivity of lysine by 1.5 times of the maximum obtained in the batch fermentation. Two-stage fermentation indicated that the kinetic model could be further extended to predict the optimal feeding strategy for fed-batch fermentation.

ANGULYDepartment of Chemical Engineering, Indian Institute ofTechnology, Kharagpur-721302, IndiaKeywords: Solid–Liquid Equilibrium, Laser Sensing, Polyethylene, Model PredictorSolubility of polyethylene in mixed xylene was determined experimentally under atmospheric pres-sure by an indigenously developed laser based technique. In this work, a PC-SAFT equation of state wasused to model solid–liquid equilibrium (SLE). With the experimental SLE data available in the litera-ture for low molecular weight n-alkanes and aromatic compounds under atmospheric pressure, the suit-ability of the developed SLE model based on the PC-SAFT equation of state was tested. Subsequently asensitivity study was performed to understand the effects of different parameters that affect the solubil-ity of polyethylene. The validated model was then used to correlate the experimentally determined solu-bility data for the polyethylene system.