• Lalitha Gottumukkala
    Biomass Researcher


A serial innovator with extensive knowledge and experience in enzymes, microbes, and fermentation. Lalitha has a PhD in life sciences (Bioprocessing and Biotechnology) from Cochin University of Science and Technology (CUSAT), India (2015). In her PhD she discovered a novel natural butanol fermenter that does not form acetone and received a business plan award from CSIR, India (2011.) She also developed strategies to co-produce solvents and organic acids and was a visiting researcher in the University of Naples for three months under a Marie-Curie fellowship grant.

Lalitha worked as a Project fellow in CSIR-NIIST on fungal enzymes production for bioethanol from agricultural residues. She led the 3-year project and developed the technology that made CSIR-NIIST qualify for scale-up and technology transfer funding.

Lalitha has postdoctoral research experience (three years) in Process Engineering at Stellenbosch University, South Africa (2014-2017). During this postdoctoral tenure, she was awarded the Claude-Leon fellowship for her project on a paper-industry biorefinery. She wrote and managed 7 research projects (worth ~€2m) and worked with several companies in South Africa to valorise waste streams.

Lalitha has worked with a wide variety of feedstocks for process and product development. Her interest is focused on feedstock evaluation for biorefineries, process development and optimisation.

Lalitha is currently working at Celignis on the ENABLING CSA project.

Expertise and Track-Record

Bioprocess Development

LD Gottumukkala has several years of experience in bioprocess development. She worked in technology transfer projects related to production of enzymes, advanced biofuels, high-value functional molecule such as biosurfactants, exopolysaccharides, arabino-xylo oligomers, volatile fatty acids etc. Her focus is on developing low-cost technologies for agro-industry and forest industry waste streams.

Her expertise in bioprocess development range from enzyme production; yeast and bacterial fermentation for fuel and high-value products; anaerobic digestion; fermentation kinetics and scale-up; Enzymatic conversions and modifications of plant polymers to functional products such as nanocellulose, hydrogels, oligomers etc.

During her career, she worked in very close association with industries such as paper mills, enzyme producers, fruit juice industry etc. to develop low-cost technologies that are technically feasible and economically viable. As a bioprocess specialist, she worked with various microorganisms and enzymes. She is very experienced in developing integrated solutions to use the resource efficiently and get the most value out of it with low CAPEX and OPEX.

Anaerobic Digestion

With her several years of bioprocess expertise, she worked on anaerobic digestion during her time at Stellenbosch University. She played a key role in setting up the anaerobic digestion testing facilities at Chemical engineering Department, Stellenbosch University. There she was responsible for the tender, design verification, procurement, commissioning, training and maintenance of seventeen 40 L scale biogas digesters. She worked on very complex streams such as paper industry sludge, fruit juice industry waste etc and developed high-rate anaerobic digestion processes that are suitable to the respective industries. For paper industry sludge and waste streams, she developed simple protocol to remove the inhibitors from the process waste water before anaerobic digestion.


She has over a decade of experience in fermentation. Her speciality is high-density, high-viscosity fermentations, Clostridial fermentation, fed-batch and continuous fermentation. She has developed fermentation process from flask level to 150 L scale. She has experience in studying the mass-transfer and conversion kinetics in the reactors and optimising the process. For recombinant yeast fermentations, she worked on on-demand feeding strategies for both methanol and glycerol feed.

She believes in co-production or sequential production of two or more products from one feedstock. Few examples are co-production of solvents, acids and hydrogen using a novel Clostridial strain; sequential production of bioethanol and biogas from paper sludge; co-production of biogas and volatile fatty acids from fruit juice industry waste streams; co-production of surfactants and biopolymers for functional applications; co-production of xylan based hydrogels and xylan oligomers, etc.

Process Design and Data Analysis

With her several years of experience in research and her close relationships with industries, she has gained knowledge in designing bespoken processes for the industries. She is expert in designing zero waste process by integrating low-cost technologies together.

She is trained in various statistical tools and is excellent in designing experiments to develop the process. Her design of experiments targets minimum number of experiments and maximum data that can help in understanding the process advantages, limitations and optimum conditions. She played a key role in designing the process and defining the process conditions for a demonstration scale paper sludge to bioethanol plant in South Africa.

The combination of process design and data analytical experience comes handy when it comes to decision making for selecting the process conditions for scale-up studies.


PhD: In Biotechnology from CSIR-NIIST (National Institute for Interdisciplinary Science and Technology), India (2015) - "Biobutanol from lignocellulosic biomass by a novel Clostridium sporogenes BE01".

MSc: In Biotechnology from Acharya Nagarjuna University, India (2007) - level 16th rank in ANUCET (Acharya Nagarjuna University common entrance test, 2005) and Distinction in the final examination (2007).

BSc: Biotechnology, Biochemistry and Chemistry from In Biotechnology from Modern Degree College affiliated to Andhra University, India (2005) - First class with 73% and Best Student Award.


Bedzo, O.K.K, Trollope K, Gottumukkala L.D, Coetzee G, Gorgens J.F. (2019) Amberlite IRA 900 versus calcium alginate in immobilization of a novel, engineered ? fructofuranosidase for short?chain fructooligosaccharide synthesis from sucrose, Biotechnology progress 35(3)

The immobilization of ? fructofuranosidase for short?chain fructooligosaccharide (scFOS) synthesis holds the potential for a more efficient use of the biocatalyst. However, the choice of carrier and immobilization technique is a key to achieving that efficiency. In this study, calcium alginate (CA), Amberlite IRA 900 (AI900) and Dowex Marathon MSA (DMM) were tested as supports for immobilizing a novel engineered ??fructofuranosidase from Aspergillus japonicus for scFOS synthesis. Several immobilization parameters were estimated to ascertain the effectiveness of the carriers in immobilizing the enzyme. The performance of the immobilized biocatalysts are compared in terms of the yield of scFOS produced and reusability. The selection of carriers and reagents was motivated by the need to ensure safety of application in the production of food?grade products. The CA and AI900 both recorded impressive immobilization yields of 82 and 62%, respectively, while the DMM recorded 47%. Enzyme immobilizations on CA, AI900 and DMM showed activity recoveries of 23, 27, and 17%, respectively. The CA, AI900 immobilized and the free enzymes recorded their highest scFOS yields of 59, 53, and 61%, respectively. The AI900 immobilized enzyme produced a consistent scFOS yield and composition for 12 batch cycles but for the CA immobilized enzyme, only 6 batch cycles gave a consistent scFOS yield. In its first record of application in scFOS production, the AI900 anion exchange resin exhibited potential as an adequate carrier for industrial application with possible savings on cost of immobilization and reduced technical difficulty.

Haigh K.F, Petersen A.M, Gottumukkala, L, Mandegari M, Naleli, K, Gorgens J.F (2018) Simulation and comparison of processes for biobutanol production from lignocellulose via ABE fermentation, Biofuels, Bioproducts and Biorefining 12(6): 1023-1036

Six conceptual process scenarios for the production of biobutanol from lignocellulosic biomass through acetone?butanol?ethanol (ABE) fermentation, using reported data on process performances, were developed with ASPEN Plus® V8.2 software. The six scenarios covered three fermentation strategies, i.e. batch separate hydrolysis and fermentation (SHF), continuous SHF, and batch simultaneous saccharification and fermentation (SSF) integrated with gas stripping (GS). The two downstream processing options considered were double?effect distillation (DD) and liquid?liquid extraction and distillation (LLE&D). It was found that the SSF?GS/DD scenario was the most energy efficient with a liquid fuel efficiency of 24% and an overall efficiency of 31%. This was also the scenario with the best economic outcome, with an internal rate of return (IRR) of 15% and net present value (NPV) of US$387 million. The SSF?GS/DD scenario was compared to a similar molasses process, based on the product flow rates, and it was found that the molasses process was more energy efficient with a gross energy value (GEV) of 23?MJ?kg1 butanol compared to ?117?MJ?kg1 butanol for the lignocellulosic process. In addition, the molasses?based process was more profitable with an IRR of 36% compared to 21%. However, the energy requirements for the molasses process were supplied from fossil fuels, whereas for the lignocellulose processes a portion of the feedstock was diverted to provide process energy. Improved environmental performance is therefore associated with the lignocellulosic process.

Vodonik M, Vrabec K, Hellwig P, Benndrof D, Sezun M, Gregori A, Gottumukkala L.D, Andersen R.C, Reichel U (2018) Valorisation of deinking sludge as a substrate for lignocellulolytic enzymes production by Pleurotus ostreatus, Journal of Cleaner production 197(1): 253-263

Disposal of waste sludges produced in large amounts in the pulp and paper industry imposes significant environmental and economical problems. One strategy to address these issues involves revalorization of paper mill sludges by their application as substrates for microbial production of biotechnologically relevant enzymes. The application of lignocellulolytic enzymes in paper, textile and bioenergy industries is encouraged in order to decrease chemicals and energy consumptions. In the following work, deinking sludge was assessed as a substrate for production of lignocellulases. Based on the results of growth and activity screenings, Pleurotus ostreatus PLAB was chosen as the most promising candidate among 30 tested strains and its secretome was further studied by quantitative enzyme assays and mass spectrometry. While endoglucanase and xylanase activities detected in P. ostreatus secretome produced on deinking sludge were similar to activities of cultures grown on other lignocellulosic substrates, average laccase activity was significantly higher (46?000 U/kg DIS). Mass spectrometry identification of the most prominent proteins in the secretome of the target strain confirmed that significant amounts of different lignin-modifying oxidases were produced on this substrate despite its low lignin content, indicating the presence of other inducible compounds. The findings of this study suggest deinking sludge may represent a good substrate for fungal production of the aforementioned enzymes with broad biotechnological applications, including bioremediation, paper and bioenergy industries.

Gottumukkala L.D, Haigh K, Gorgens J (2017) Trends and advances in conversion of lignocellulosic biomass to biobutanol: microbes, bioprocesses and industrial viability, Renewable and Sustainable Energy Reviews 76: 963-973

Biobutanol has gained attention as an alternative renewable transportation fuel for its superior fuel properties and widespread applications in chemical industry, primarily as a solvent. Conventional butanol fermentation has drawbacks that include strain degeneration, end-product toxicity, by-product formation, low butanol concentrations and high substrate cost. The complexity of Clostridium physiology and close control between sporulation phase and ABE fermentation has made it demanding to develop industrially potent strains. In addition to the isolation and engineering of superior butanol producing bacteria, the development of advanced cost-effective technologies for butanol production from feedstock like lignocellulosic biomass has become the primary research focus. High process costs associated with complex feedstocks, product toxicity and low product concentrations are few of the several bioprocess challenges involved in biobutanol production. The article aims to assess the challenges in lignocellulosic biomass to biobutanol conversion and identify key process improvements that can make biobutanol commercially viable.

Gottumukka L.D, Haigh K, Collard F.X, Van Rensburg E, Gorgens J (2016) Opportunities and prospects of biorefinery-based valorisation of pulp and paper sludge, Bioresource technology 215: 37-49

The paper and pulp industry is one of the major industries that generate large amount of solid waste with high moisture content. Numerous opportunities exist for valorisation of waste paper sludge, although this review focuses on primary sludge with high cellulose content. The most mature options for paper sludge valorisation are fermentation, anaerobic digestion and pyrolysis. In this review, biochemical and thermal processes are considered individually and also as integrated biorefinery. The objective of integrated biorefinery is to reduce or avoid paper sludge disposal by landfilling, water reclamation and value addition. Assessment of selected processes for biorefinery varies from a detailed analysis of a single process to high level optimisation and integration of the processes, which allow the initial assessment and comparison of technologies. This data can be used to provide key stakeholders with a roadmap of technologies that can generate economic benefits, and reduce carbon wastage and pollution load.

Boshoff A, Gottumukka L.D, Van Rensburg E, Gorgens J (2016) Paper sludge (PS) to bioethanol: Evaluation of virgin and recycle mill sludge for low enzyme, high-solids fermentationl, Bioresource technology 23: 103-111

Paper sludge (PS) from the paper and pulp industry consists primarily of cellulose and ash and has significant potential for ethanol production. Thirty-seven PS samples from 11 South African paper and pulp mills exhibited large variation in chemical composition and resulting ethanol production. Simultaneous saccharification and fermentation (SSF) of PS in fed-batch culture was investigated at high solid loadings and low enzyme dosages. Water holding capacity and viscosity of the PS influenced ethanol production at elevated solid loadings of PS. High viscosity of PS from virgin pulp mills restricted the solid loading to 18% (w/w) at an enzyme dosage of 20 FPU/gram dry PS (gdPS), whereas an optimal solid loading of 27% (w/w) was achieved with corrugated recycle mill PS at 11 FPU/gdPS. Ethanol concentration and yield of virgin pulp and corrugated recycle PS were 34.2 g/L at 66.9% and 45.5 g/L at 78.2%, respectively.

Robus C.L.L, Gottumukkala, L.D, Van Rensburg E, Gorgens J.F. (2016) Feasible process development and techno-economic evaluation of paper sludge to bioethanol conversion: South African paper mills scenario, Renewable energy 92: 333-345

Paper sludge samples collected from recycling mills exhibited high ash content in the range of 54.59%–65.50% and glucose concentrations between 21.97% and 31.11%. Washing the sludge reduced the total ash content to between 10.7% and 19.31% and increased the concentration of glucose, xylose and lignin. Samples were screened for ethanol production and fed-batch simultaneous saccharification and fermentation (SSF) was optimised for the washed samples that resulted in highest and lowest ethanol concentrations. Maximum ethanol concentrations of 57.31 g/L and 47.72 g/L (94.07% and 85.34% of the maximum theoretical yield, respectively) was predicted for high and low fermentative potential samples, respectively, and was experimentally achieved with 1% deviation. A generic set of process conditions were established for the conversion of high ash-containing paper sludge to ethanol. Techno-economic analysis based on three different revenue scenarios, together with Monte Carlo analysis revealed 95% probability of achieving IRR values in excess of 25% at a paper sludge feed rate of 15 t/d. Feed rates of 30 t/d and 50 t/d exhibited a cumulative probability of 100%. This study presents the technical feasibility and economic viability of paper mills expansion towards bioethanol production from paper sludge.

Gottumukkala L.D. Gorgens J.F (2016) Biobutanol production from lignocellulosics, Biofuels Production and future perspectives, Taylor & Francis group

Next-generation biofuels from renewable sources have gained interest among research investigators, industrialists, and governments due to major concerns on the volatility of oil prices, climate change, and depletion of oil reserves. Biobutanol has drawn signicant attention as an alternative transportation fuel due to its superior fuel properties over ethanol. e advantages of butanol are its high energy content, better blending with gasoline, less hydroscopic nature, lower volatility, direct use in convention engines, low corrosiveness, etc. Butanol production through (acetone, butanol, and ethanol) ABE fermentation is a well-established process, but it has several drawbacks like feedstock cost, strain degeneration, product toxicity, and low product concentrations. Lignocellulosic biomass is considered as the most abundant, renewable, low-cost feedstock for biofuels. Production of butanol from lignocellulosic biomass is more complicated due to the recalcitrance of feedstock and inhibitors generated during the pretreatment and hydrolysis process. Advanced fermentation and product recovery techniques are being researched to make biobutanol industrially viable.

Sajna K.P, Sukumaran R.K, Gottumukkala L.D, Pandey A (2015) Crude oil biodegradation aided by biosurfactants from Pseudozyma sp. NII 08165 or its culture broth, Bioresource technology 191: 133-139

The aim of this work was to evaluate the biosurfactants produced by the yeast Pseudozyma sp. NII 08165 for enhancing the degradation of crude oil by a model hydrocarbon degrading strain, Pseudomonas putida MTCC 1194. Pseudozyma biosurfactants were supplemented at various concentrations to the P. putida culture medium containing crude oil as sole carbon source. Supplementation of the biosurfactants enhanced the degradation of crude oil by P. putida; the maximum degradation of hydrocarbons was observed with a 2.5 mg L?1 supplementation of biosurfactants. Growth inhibition constant of the Pseudozyma biosurfactants was 11.07 mg L?1. It was interesting to note that Pseudozyma sp. NII 08165 alone could also degrade diesel and kerosene. Culture broth of Pseudozyma containing biosurfactants resulted up to ?46% improvement in degradation of C10–C24 alkanes by P. putida. The enhancement in degradation efficiency of the bacterium with the culture broth supplementation was even more pronounced than that with relatively purer biosurfactants.

Gottumukkala L.D, Sukumaran R.K. Mohan S.V. Valappil S.K. Sarkar O, Pandey A (2015) Rice straw hydrolysate to fuel and volatile fatty acid conversion by Clostridium sporogenes BE01: bio-electrochemical analysis of the electron transport mediators involved, Green chemistry 17(5): 3047-3058

Clostridium sporogenes BE01, a non-acetone forming butanol producer, can produce hydrogen and volatile fatty acids (VFAs) during butanol fermentation from rice straw hydrolysate. Bio-electrochemical analysis revealed the changes that occurred in the redox microenvironment and electron transport mediators during fermentation at different pH and CaCO3 concentrations. CaCO3 played a very important role in enhancing the production of hydrogen, volatile fatty acids and solvents by stimulating the changes in the electron transport system. The electron transport system mediated by NAD/NADH, flavins, Fe–S clusters, protein bound FAD, and cytochrome complex in C. sporogenes BE01 was analysed by cyclic voltammetry (CV). Electrokinetic analysis revealed that the favorability for redox reactions increased with an increase in pH, and the polarization resistance reduced significantly with CaCO3 supplementation.

Sajna K.V, Gottumukkala L.D, Sukumaran R.K, Pandey A. (2015) White biotechnology in cosmetics, Industrial Biorefineries & White Biotechnology, Elsevier
Thomas L, Joseph A, Gottumukkala L.D. (2014) Xylanase and cellulase systems of Clostridium sp.: an insight on molecular approaches for strain improvement, Bioresource technology 158: 343-350

Bioethanol and biobutanol hold great promise as alternative biofuels, especially for transport sector, because they can be produced from lignocellulosic agro-industrial residues. From techno-economic point of view, the bioprocess for biofuels production should involve minimal processing steps. Consolidated bioprocessing (CBP), which combines various processing steps such as pretreatment, hydrolysis and fermentation in a single bioreactor, could be of great relevance for the production of bioethanol and biobutanol or solvents (acetone, butanol, ethanol), employing clostridia. For CBP, Clostridium holds best promise because it possesses multi-enzyme system involving cellulosome and xylanosome, which comprise several enzymes such as cellulases and xylanases. The aim of this article was to review the recent developments on enzyme systems of clostridia, especially xylanase and cellulase with an effort to analyse the information available on molecular approaches for the improvement of strains with ultimate aim to improve the efficiencies of hydrolysis and fermentation.

Gottumukkala L.D, Parameswaran B, Valappil S.K, Pandey A (2014) Growth and butanol production by Clostridium sporogenes BE01 in rice straw hydrolysate: kinetics of inhibition by organic acids and the strategies for their removal, Biomass Conversion and Biorefinery 4(3): 277-283

Growth inhibition kinetics of a novel non-acetone forming butanol producer, Clostridium sporogenes BE01, was studied under varying concentrations of acetic and formic acids in rice straw hydrolysate medium. Both the organic acids were considered as inhibitors as they could inhibit the growth of the bacterium, and the inhibition constants were determined to be 1.6 and 0.76 g/L, respectively, for acetic acid and formic acid. Amberlite resins—XAD 4, XAD 7, XAD 16, and an anion exchange resin—Seralite 400 were tested for the efficient removal of these acidic inhibitors along with minimal adsorption of sugars and essential minerals present in the hydrolysate. Seralite 400 was an efficient adsorbent of acids, with minimal affinity towards minerals and sugars. Butanol production was evaluated to emphasize the effect of minerals loss and acids removal by the resins during detoxification.

Gottumukkala, L. D, Valappi, S. K. (2013) Biobutanol production from rice straw by a non acetone producing Clostridium sporogenes BE01, Bioresource Technology 145: 182-187

Biobutanol from lignocellulosic biomass has gained much attention due to several advantages over bioethanol. Though microbial production of butanol through ABE fermentation is an established technology, the use of lignocellulosic biomass as feedstock presents several challenges. In the present study, biobutanol production from enzymatic hydrolysate of acid pretreated rice straw was evaluated using Clostridium sporogenes BE01. This strain gave a butanol yield of 3.43 g/l and a total solvent yield of 5.32 g/l in rice straw hydrolysate supplemented with calcium carbonate and yeast extract. Hydrolysate was analyzed for the level of inhibitors such as acetic acid, formic acid and furfurals which affect the growth of the organism and in turn ABE fermentation. Methods for preconditioning the hydrolysate to remove toxic end products were done so as to improve the fermentation efficiency. Conditions of ABE fermentation were fine tuned resulting in an enhanced biobutanol reaching 5.52 g/l.

Gottumukkala L.D, Parameswaran B, Valappil S.K, Mathiyazhakan, K (2013) Biobutanol production from rice straw by a non acetone producing Clostridium sporogenes BE01, Bioresource technology 145: 182-187

Biobutanol from lignocellulosic biomass has gained much attention due to several advantages over bioethanol. Though microbial production of butanol through ABE fermentation is an established technology, the use of lignocellulosic biomass as feedstock presents several challenges. In the present study, biobutanol production from enzymatic hydrolysate of acid pretreated rice straw was evaluated using Clostridium sporogenes BE01. This strain gave a butanol yield of 3.43 g/l and a total solvent yield of 5.32 g/l in rice straw hydrolysate supplemented with calcium carbonate and yeast extract. Hydrolysate was analyzed for the level of inhibitors such as acetic acid, formic acid and furfurals which affect the growth of the organism and in turn ABE fermentation. Methods for preconditioning the hydrolysate to remove toxic end products were done so as to improve the fermentation efficiency. Conditions of ABE fermentation were fine tuned resulting in an enhanced biobutanol reaching 5.52 g/l.

Sajna K.V, Sukumaran R.K, Gottumukkala L.D, Jayamurthy H, Dhar K.S (2013) Studies on structural and physical characteristics of a novel exopolysaccharide from Pseudozyma sp. NII 08165, International Journal of Biological Macromolecules 59: 84-89
Singhania R.R, Sukumaran R.K, Rajasree K.P, Mathew A, Gottumukkala L.D, Pandey A (2011) Properties of a major ?-glucosidase-BGL1 from Aspergillus niger NII-08121 expressed differentially in response to carbon sources, Process Biochemistry 46(7): 1521-1524

Aspergillus niger NII-08121/MTCC 7956 exhibited differences in expression of ?-glucosidase (BGL) in response to carbon sources provided in the medium. Activity staining with methyl umbelliferyl ?-d-glucopyranoside (MUG) indicated that four different isoforms of BGL were expressed when A. niger was grown under submerged fermentation with either lactose or cellulose, whereas only two were expressed when wheat bran or rice straw was used as the carbon source. Among the four isoforms of BGL expressed during lactose supplementation, two were found to retain 92% and 82% activity respectively in presence of 250 mM glucose in the MUG assay. The major ?-glucosidase (BGL1) was purified to homogeneity by electro elution from a Native PAGE gel. The purified 120 kDa protein was active at 50 °C and was stable for 48 h without any loss of activity. The optimum pH and temperature were 4.8 and 70 °C respectively.

Sukumaran R.K, Gottumukkala L.D, Rajasree K.P, Alex D, Pandey A (2011) Butanol fuel from biomass: Revisiting ABE fermentation, Biofuels, Elsevier

ABE (Acetone-Butanol-Ethanol) fermentations were next only to ethanol fermentations and used to be a major industry until 1960s. Later, biological route for butanol production lost its importance owing to competition from petrochemical route, and today there is a renewed interest in ABE fermentation due to increased concerns over petroleum depletion and the increased pollution due to burning of petroleum fuels. Though the ABE fermentation process used to be operational decades back, the same technologies are not applicable today due to the lack of cost effectiveness and the nonavailability of conventional raw materials. The most feasible feedstock for butanol seems to be lignocellulose, but the problems plaguing bioethanol are also applicable for biobutanol. However, the future for biobutanol seemsbright since the Clostridia that produce ABE are capable of utilizing a range of carbon sources for growth and solvent production and also are not inhibited by the sugar degradation products generated during biomass pretreatment are being developed. Meanwhile, in the short term, advanced fermentation technologies are being developed by the expert groups which tackle problems such as low cell density, viability, and solvent sensitivity by modulations in the methods of carbon feeding, mode of culture, and in situ removal and recovery of solvents. These efforts may be developed into commercially viable technologies.

Parameswaran, B, Raveendran S, Singhania, R.R, Surender V, L Devi, Nagalakshmi S, Kurien N, Sukumaran R.K, Pandey A. (2010) Bioethanol production from rice straw: an overview, Bioresource technology 101(13): 4767-4774

Rice straw is an attractive lignocellulosic material for bioethanol production since it is one of the most abundant renewable resources. It has several characteristics, such as high cellulose and hemicelluloses content that can be readily hydrolyzed into fermentable sugars. But there occur several challenges and limitations in the process of converting rice straw to ethanol. The presence of high ash and silica content in rice straw makes it an inferior feedstock for ethanol production. One of the major challenges in developing technology for bioethanol production from rice straw is selection of an appropriate pretreatment technique. The choice of pretreatment methods plays an important role to increase the efficiency of enzymatic saccharification thereby making the whole process economically viable. The present review discusses the available technologies for bioethanol production using rice straw.

Aswathy U.S, Sukumaran R.K, Devi G.L, Rajasree K.P, Singhania R.R. (2010) Bio-ethanol from water hyacinth biomass: an evaluation of enzymatic saccharification strategy, Bioresource technology 101(3): 925-930

Biomass feedstock having less competition with food crops are desirable for bio-ethanol production and such resources may not be localized geographically. A distributed production strategy is therefore more suitable for feedstock like water hyacinth with a decentralized availability. In this study, we have demonstrated the suitability of this feedstock for production of fermentable sugars using cellulases produced on site. Testing of acid and alkali pretreatment methods indicated that alkali pretreatment was more efficient in making the sample susceptible to enzyme hydrolysis. Cellulase and ?-glucosidase loading and the effect of surfactants were studied and optimized to improve saccharification. Redesigning of enzyme blends resulted in an improvement of saccharification from 57% to 71%. A crude trial on fermentation of the enzymatic hydrolysate using the common baker’s yeast Saccharomyces cerevisiae yielded an ethanol concentration of 4.4 g/L.