Biofuels from inulin-rich feedstocks: A comprehensive review.

Biofuels are considered as a pre-eminent alternate to fossil fuels to meet the demand of future energy supply in a sustainable manner. Conventionally, they are produced from lignocellulosic raw materials. Saccharification of lignocellulosic raw materials for bioethanol production is a cumbersome process as compared to inulin-rich feedstocks. Various inulin-rich feedstocks, viz. jerusalem artichoke, chicory, dahlia, asparagus sp., etc. has also been exploited for the production of biofuels, viz. bioethanol, acetone, butanol, etc. The ubiquitous availability of inulin-rich feedstocks and presence of large amount of inulin makes them a robust substrate for biofuels production. Different strategies, viz. separate hydrolysis and fermentation, simultaneous saccharification and fermentation and consolidated bioprocessing have been explored for the conversion of inulin-rich feedstocks into biofuels. These bioprocess strategies are simple and efficient. The present review elaborates the prospective of inulin-rich feedstocks for biofuels production. Bioprocess strategies exploited for the conversion of inulin-rich feedstocks have also been highlighted.

Solvothermal conversion of spent aromatic waste to ethyl glucosides.

On-farm extraction of commercially important essential oil from aromatic crops generates huge spent aromatic waste. This massive waste is often disposed in the unregulated landfills or burned in the open air to vacate the fields. Hence, a new method for processing of aromatic spent waste has been developed to obtain platform chemicals, such as, xylose and ethyl glucosides. The thermochemical liquefaction of acid pre-treated palmarosa (cymbopogon martini) biomass furnished a mixture of ethyl glucopyranosides in good yield (∼17 wt% relative to biomass) and selectivity (∼77%) by heating with p-cymen-2-sulphonic acid (p-CSA) in the presence of ethanol as a solvent. The detection, quantification and isolation of ethyl glucosides may provide a new application of spent aromatic biomass for use as a feed stock in the production of value added chemicals.

New Continuous Process for the Production of Lipopeptide Biosurfactants in Foam Overflowing Bioreactor.

In this work, an original culture process in bioreactor named overflowing continuous culture (O-CC) was developed to produce and recover continuously mycosubtilin, a lipopeptide antifungal biosurfactant of major interest. The lipopeptide production was first investigated in shake conical flasks in different culture media [ammonium citrate sucrose (ACS), Difco sporulation medium (DSM), and Landy], followed by a pH condition optimization using 3-(N-morpholino)propanesulfonic acid (MOPS) and 2-(N-morpholino)ethanesulfonic acid (MES) buffered media. A simple theoretical modeling of the biomass evolution combined with an experimental setup was then proposed for O-CC processed in stirred tank reactor at laboratory scale. Seven O-CC experiments were done in modified Landy medium at the optimized pH 6.5 by applying dilution rates comprised between 0.05 and 0.1 h-1. The O-CC allowed the continuous recovery of the mycosubtilin contained in the foam overflowing out of the reactor, achieving a remarkable in situ product removal superior to 99%. The biomass concentration in the overflowing foam was found to be twofold lower than the biomass concentration in the reactor, relating advantageously this process to a continuous one with biomass feedback. To evaluate its performances regarding the type of lipopeptide produced, the O-CC process was tested with strain BBG116, a mycosubtilin constitutive overproducing strain that also produces surfactin, and strain BBG125, its derivative strain obtained by deleting surfactin synthetase operon. At a dilution rate of 0.1 h-1, specific productivity of 1.18 mg of mycosubtilin⋅g-1(DW)⋅h-1 was reached. Compared with other previously described bioprocesses using almost similar culture conditions and strains, the O-CC one allowed an increase of the mycosubtilin production rate by 2.06-fold.

Comprehensive assessment of 2G bioethanol production.

The advancements in second-generation bioethanol produced from lignocellulosic biomass, such as crops residues, woody crops or energy grasses are gaining momentum. Though, they are still representing less than 3% of total bioethanol production, the GHG reduction potential is higher than for 1G-bioethanol. The environmental impacts of bioethanol production are totally dependent on feedstock availability and conversion technology. The biochemical conversion route must overcome several technological and economical challenges such as pre-treatment, fermentation, hydrolysis process and separation. A completely mature technology is still to be developed and must adapted to the nature of the feedstock. Nevertheless, using process simulation software, Life Cycle Assessment and integrating the different steps of bioresource harvesting and treatment processes, including the energy balances and the water requirements, it is shown that 2G bioethanol production will reduce environmental impacts provided the evaluation addresses a long-time perspective, including all conversion steps and the regeneration of the bioresource.

Optimization of limonene biotransformation for the production of bulk amounts of α-terpineol.

The biotransformation of R-(+)-limonene into high concentrations of R-(+)-α-terpineol by Sphingobium sp. was investigated in order to optimize the main process variables (pH, biocatalyst concentration, substrate concentration, temperature and agitation). This strategy comprised the screening of variables by a Plackett-Burman design followed by a Central Composite Design. The statistical analysis showed that the optimal α-terpineol production were at 28 °C and pH 7.0, with a limonene concentration of 350 g/L of organic phase agitation of 200 rpm and a biocatalyst concentration of 2.8 g/L of aqueous phase (OD600 = 8). Further trials showed that the R-(+)-α-terpineol concentration was higher (240 g/L after 96 h) when using a ratio of 1:3 (v.v-1) of organic:aqueous phases. However, the total production and yield (in terms of biomass) of α-terpineol would be maximized for an aqueous:organic ratio of 1:1. The experimental design optimization adopted herein was an effective tool for this type of study.

Biotechnological applications of inulin-rich feedstocks.

Inulin is a naturally occurring second largest storage polysaccharide with a wide range of applications in pharmaceutical and food industries. It is a robust polysaccharide which consists of a linear chain of ß-2, 1-linked-d-fructofuranose molecules terminated with α-d-glucose moiety at the reducing end. It is present in tubers, bulbs and tuberous roots of more than 36,000 plants belonging to both monocotyledonous and dicotyledonous families. Jerusalem artichoke, chicory, dahlia, asparagus, etc. are important inulin-rich plants. Inulin is a potent substrate and inducer for the production of inulinases. Inulin/inulin-rich feedstocks can be used for the production of fructooligosaccharides and high-fructose syrup. Additionally, inulin-rich feedstocks can also be exploited for the production of other industrially important products like acetone, butanol, bioethanol, single cell proteins, single cell oils, 2, 3-butanediol, sorbitol, mannitol, etc. Current review highlights the biotechnological potential of inulin-rich feedstocks for the production of various industrially important products.

Hydrogen production by dark fermentation from pre-fermented depackaging food wastes.

In this study, a specific fraction of food waste, i.e. depackaging waste, was studied as substrate for hydrogen production by dark fermentation. During storage and transport of this liquid mixture, inhibitory compounds like acids or alcohol might be produced by endogenous flora. A factorial fractional design based on the composition of the substrate was used to determine the best condition to convert this substrate into hydrogen. First results indicated that the consortium used might convert high quantity of lactate into hydrogen. A batch culture confirmed that lactate was used as the main carbon source and a global yield of 0.4molH2·mollactate-1 was obtained. This study demonstrated the ability of the consortium tested to convert different carbon sources (carbohydrates or lactate) with good efficiency. These data represented an important parameter in the prospect of using an industrial substrate whose composition is liable to vary according to the conditions of storage and transport.

Purification and characterization of two isoforms of exoinulinase from Penicillium oxalicum BGPUP-4 for the preparation of high fructose syrup from inulin.

Two exoinulinases, Exo-I and Exo-II from the culture broth of Penicillium oxalicum BGPUP-4 was purified using three-step purification method i.e., isopropanol precipitation, Q-Sepharose and Sephadex G-100 column chromatography. The molecular weight of Exo-I and Exo-II was determined to be 64.85 kDa and 32.54 kDa, respectively using MALDI-TOF. Exo-I and Exo-II showed high specificity for inulin and their respective Vmax/Km ratio was 3.74 and 7.20. Besides, both the inulinases also displayed specificity for lactose, sucrose and raffinose. Exo-I and Exo-II were stable at a pH range of 4.0-8.0 with pH optima 5.0. Optimal temperature for both the inulinases was 55 °C, and both the isoforms retained approximately 50% of their activity up to 70 °C. Ag+, Hg2+, Ba2+, Cu2+ and Ca2+ ions shown stimulatory effect on inulinases activity, while Fe2+, Mn2+, Co2+and EDTA completely inhibited enzyme activity. Purified enzyme was successfully used for the preparation of high fructose syrup from inulin.

Solid-State Fermentation of Carrot Pomace for the Production of Inulinase by Penicillium oxalicum BGPUP-4.

Inulinases are an important class of industrial enzymes which are used for the production of high-fructose syrup and fructooligosaccharides. Inulin, a polyfructan, is generally employed for the production of inulinase, which is a very expensive substrate. A number of agroindustrial residues have been used for cost-effective production of inulinases. In the present study, carrot pomace was selected as a substrate for the production of inulinase by Penicillium oxalicum BGPUP-4 in solid-state fermentation. Carrot pomace is one of the good substrates for bioprocesses, because it is rich in soluble and insoluble carbohydrates. A central composite rotatable design (CCRD) used in response surface methodology was employed for the optimal production of inulinase from carrot pomace. Using CCRD, 15 runs were practiced to optimize the range of three independent variables: moisture content (70-90%), incubation time (4-6 days) and pH (5.0-7.0) for inulinase production. Carrot pomace supplemented with 0.5% inulin as an inducer, 0.2% NH4H2PO4, 0.2% NaNO3, 0.2% KH2PO4, 0.05% MgSO4·7H2O and 0.001% FeSO4·7H2O was used for the production of inulinase in solid-state fermentation at 30 °C. Inulinase production (322.10 IU per g of dry substrate) was obtained under the optimized conditions, i.e. moisture content of 90%, incubation time 4 days and pH=7.0. The corresponding inulinase/invertase (I/S) ratio (3.38) was also high, which indicates the inulolytic nature of the enzyme. Multiple correlation coefficients R for inulinase production and I/S ratio were 0.9995 and 0.9947, respectively. The R value very close to one indicates an excellent correlation between experimental and predicted results.

Biocatalytic strategies for the production of high fructose syrup from inulin.

The consumption of natural and low calorie sugars has increased enormously from the past few decades. To fulfil the demands, the production of healthy sweeteners as an alternative to sucrose has recently received considerable interest. Fructose is the most health beneficial and safest sugar amongst them. It is generally recognised as safe (GRAS) and has become an important food ingredient due its sweetening and various health promising functional properties. Commercially, high fructose syrup is prepared from starch by multienzymatic process. Single-step enzymatic hydrolysis of inulin using inulinase has emerged as an alternate to the conventional approach to reduce complexity, time and cost. The present review, outlines the enzymatic strategies used for the preparation of high fructose syrup from inulin/inulin-rich plant materials in batch and continuous systems, and its conclusions.

Carbon dioxide capture, storage and production of biofuel and biomaterials by bacteria: A review.

Due to industrialization and urbanization, as humans continue to rely on fossil fuels, carbon dioxide (CO2) will inevitably be generated and result in an increase of Global Warming Gases (GWGs). However, their prospect is misted up because of the environmental and economic intimidation posed by probable climate shift, generally called it as the "green house effect". Among all GWGs, the major contributor in greenhouse effect is CO2. Mitigation strategies that include capture and storage of CO2 by biological means may reduce the impact of CO2 emissions on environment. The biological CO2 sequestration has significant advantage, since increasing atmospheric CO2 level supports productivity and overall storage capacity of the natural system. This paper reviews CO2 sequestration mechanism in bacteria and their pathways for production of value added products such as, biodiesel, bioplastics, extracellular polymeric substance (EPS), biosurfactants and other related biomaterials.

Cloning and Characterization of the Gene Encoding Alpha-Pinene Oxide Lyase Enzyme (Prα-POL) from Pseudomonas rhodesiae CIP 107491 and Production of the Recombinant Protein in Escherichia coli.

The alpha-pinene oxide lyase (Prα-POL) from Pseudomonas rhodesiae CIP107491 belongs to catabolic alpha-pinene degradation pathway. In this study, the gene encoding Prα-POL has been identified using mapping approach combined to inverse PCR (iPCR) strategy. The Prα-POL gene included a 609-bp open reading frame encoding 202 amino acids and giving rise to a 23.7 kDa protein, with a theoretical isoelectric point (pI) of 5.23. The amino acids sequence analysis showed homologies with those of proteins with unknown function from GammaProteobacteria group. Identification of a conserved domain in amino acid in positions 18 to 190 permitted to classify Prα-POL among the nuclear transport factor 2 (NTF2) protein superfamily. Heterologous expression of Prα-POL, both under its native form and with a histidin tag, was successfully performed in Escherichia coli, and enzymatic kinetics were analyzed. Bioconversion assay using recombinant E. coli strain allowed to reach a rate of isonovalal production per gramme of biomass about 40-fold higher than the rate obtained with P. rhodesiae.

Biodiesel production from lipid of carbon dioxide sequestrating bacterium and lipase of psychrotolerant Pseudomonas sp. ISTPL3 immobilized on biochar.

An extracellular lipase was purified and characterized from psychrotolerant bacterium Pseudomonas sp. ISTPL3 isolated from Pangong lake. Lipase was purified by sequential methods of ammonium sulphate precipitation, dialysis, DEAE-cellulose ion exchange chromatography and Sephadex G-100 gel filtration chromatography, resulting in a purification fold of 6.53 and yield of 5.45%. The molecular weight was approximately 31kDa. The purified lipase was used for transesterification of lipids produced by oleaginous chemolithotrophic bacterium Serratia sp. ISTD04 for production of biodiesel. Upon biochemical characterization, lipase was found to be alkalophilc, thermostable, active in organic polar solvents and sensitive to detergents. Further, lipase was immobilized on activated biochar to assess its transesterification efficiency during biodiesel production. Immobilized lipase gave the highest yield of fatty acid methyl esters (FAMEs) (92.23%)>unimmobilized lipase>NaOH. The immobilized lipase was assessed for its reusability and retained 75.11% of its activity after 3 cycles of biodiesel production.

Microalgal hydrogen production - A review.

Bio-hydrogen from microalgae including cyanobacteria has attracted commercial awareness due to its potential as an alternative, reliable and renewable energy source. Photosynthetic hydrogen production from microalgae can be interesting and promising options for clean energy. Advances in hydrogen-fuel-cell technology may attest an eco-friendly way of biofuel production, since, the use of H2 to generate electricity releases only water as a by-product. Progress in genetic/metabolic engineering may significantly enhance the photobiological hydrogen production from microalgae. Manipulation of competing metabolic pathways by modulating the certain key enzymes such as hydrogenase and nitrogenase may enhance the evolution of H2 from photoautotrophic cells. Moreover, biological H2 production at low operating costs is requisite for economic viability. Several photobioreactors have been developed for large-scale biomass and hydrogen production. This review highlights the recent technological progress, enzymes involved and genetic as well as metabolic engineering approaches towards sustainable hydrogen production from microalgae.

Characterization of carbon dioxide concentrating chemolithotrophic bacterium Serratia sp. ISTD04 for production of biodiesel.

Proteomics and metabolomics analysis has become a powerful tool for characterization of microbial ability for fixation of Carbon dioxide. Bacterial community of palaeoproterozoic metasediments was enriched in the shake flask culture in the presence of NaHCO3. One of the isolate showed resistance to NaHCO3 (100mM) and was identified as Serratia sp. ISTD04 by 16S rRNA sequence analysis. Carbon dioxide fixing ability of the bacterium was established by carbonic anhydrase enzyme assay along with proteomic analysis by LC-MS/MS. In proteomic analysis 96 proteins were identified out of these 6 protein involved in carbon dioxide fixation, 11 in fatty acid metabolism, indicating the carbon dioxide fixing potency of bacterium along with production of biofuel. GC-MS analysis revealed that hydrocarbons and FAMEs produced by bacteria within the range of C13-C24 and C11-C19 respectively. Presence of 59% saturated and 41% unsaturated organic compounds, make it a better fuel composition.

Development of a submerged anaerobic membrane bioreactor for concurrent extraction of volatile fatty acids and biohydrogen production.

The aim of this work was to study an externally-submerged membrane bioreactor for the cyclic extraction of volatile fatty acids (VFAs) during anaerobic fermentation, combining the advantages of submerged and external technologies for enhancing biohydrogen (BioH2) production from agrowaste. Mixing and transmembrane pressure (TMP) across a hollow fiber membrane placed in a recirculation loop coupled to a stirred tank were investigated, so that the loop did not significantly modify the hydrodynamic properties in the tank. The fouling mechanism, due to cake layer formation, was reversible. A cleaning procedure based on gas scouring and backwashing with the substrate was defined. Low TMP, 10(4)Pa, was required to achieve a 3Lh(-1)m(-2) critical flux. During fermentation, BioH2 production was shown to restart after removing VFAs with the permeate, so as to enhance simultaneously BioH2 production and the recovery of VFAs as platform molecules.

Improvement and modeling of culture parameters to enhance biomass and lipid production by the oleaginous yeast Cryptococcus curvatus grown on acetate.

The improvement of culture parameters for lipid production from acetate as carbon source was investigated using the oleaginous yeast Cryptococcus curvatus. A new pH regulation system dispensing acetate was developed for fed-batch culture and allowed obtaining nearly 80 g/L biomass within 60 h with a maximal growth rate of 0.28 h(-1). A biological model was developed from experimental data. The influence of three C/N ratios of 300, 500 and 900 were tested during a multi-phases process on lipid accumulation. The C/N ratio of 300 was reported to be the most suitable for lipid storage. No significant increase of lipids content was obtained with higher value. A maximal content of 60% DCW of lipid was obtained. The determination of fatty acids profiles of the microbial oils has confirmed that the valorization of acetate by microbial oils production was a promising perspective.

Favouring butyrate production for a new generation biofuel by acidogenic glucose fermentation using cells immobilised on γ-alumina.

The effect of γ-alumina as a fermentation advancing tool and as carrier for culture immobilisation, regarding VFAs and ethanol production during acidogenic fermentation of glucose, was examined at various process conditions (sugar concentration, pH) and operation modes (continuous with and without effluent recirculation and batch). The results showed that at high initial pH (8.9) the continuous acidogenic fermentation of glucose led to high yields of VFAs and favoured the accumulation of butyric acid. The batch process on the other hand at pH 6.5, favoured the ethanol-type fermentation. The results indicate that in the frame of technology development for new generation biofuels, using γ-alumina as a process advancing tool at optimum process conditions (pH, initial glucose concentration and mode of operation), the produced VFAs profile and ethanol concentration may be manipulated.

Economic process to produce biohydrogen and volatile fatty acids by a mixed culture using vinasse from sugarcane ethanol industry as nutrient source.

This work evaluates the potential of vinasse (a waste obtained at the bottom of sugarcane ethanol distillation columns) as nutrient source for biohydrogen and volatile fatty acids production by means of anaerobic consortia. Two different media were proposed, using sugarcane juice or molasses as carbon source. The consortium LPBAH1 was selected for fermentation of vinasse supplemented with sugarcane juice, resulting in a higher H2 yield of 7.14 molH2 molsucrose(-1) and hydrogen content in biogas of approx. 31%, while consortium LPBAH2 resulted in 3.66 molH2/molsucrose and 32.7% hydrogen content in biogas. The proposed process showed a rational and economical use for vinasse, a mandatory byproduct of the renewable Brazilian energy matrix.

Cellulase activity mapping of Trichoderma reesei cultivated in sugar mixtures under fed-batch conditions.

BACKGROUND: On-site cellulase production using locally available lignocellulosic biomass (LCB) is essential for cost-effective production of 2nd-generation biofuels. Cellulolytic enzymes (cellulases and hemicellulases) must be produced in fed-batch mode in order to obtain high productivity and yield. To date, the impact of the sugar composition of LCB hydrolysates on cellulolytic enzyme secretion has not been thoroughly investigated in industrial conditions. RESULTS: The effect of sugar mixtures (glucose, xylose, inducer) on the secretion of cellulolytic enzymes by a glucose-derepressed and cellulase-hyperproducing mutant strain of Trichoderma reesei (strain CL847) was studied using a small-scale protocol representative of the industrial conditions. Since production of cellulolytic enzymes is inducible by either lactose or cellobiose, two parallel mixture designs were performed separately. No significant difference between inducers was observed on cellulase secretion performance, probably because a common induction mechanism occurred under carbon flux limitation. The characteristics of the enzymatic cocktails did not correlate with productivity, but instead were rather dependent on the substrate composition. Increasing xylose content in the feed had the strongest impact. It decreased by 2-fold cellulase, endoglucanase, and cellobiohydrolase activities and by 4-fold ß-glucosidase activity. In contrast, xylanase activity was increased 6-fold. Accordingly, simultaneous high ß-glucosidase and xylanase activities in the enzymatic cocktails seemed to be incompatible. The variations in enzymatic activity were modelled and validated with four fed-batch cultures performed in bioreactors. The overall enzyme production was maintained at its highest level when substituting up to 75% of the inducer with non-inducing sugars. CONCLUSIONS: The sugar substrate composition strongly influenced the composition of the cellulolytic cocktail secreted by T. reesei in fed-batch mode. Modelling can be used to predict cellulolytic activity based on the sugar composition of the culture-feeding solution, or to fine tune the substrate composition in order to produce a desired enzymatic cocktail.