Ramkumar B. Nair

Valorization of sugar-to-ethanol process waste vinasse : A novel biorefinery approach using edible ascomycetes filamentous fungi

The aim of the present work was to study the integration of edible ascomycetes filamentous fungi into the existing sugar- or molasses-to-ethanol processes, to grow on vinasse or stillage and produce ethanol and protein-rich fungal biomass. Two fungal strains, Neurospora intermedia and Aspergillus oryzae were examined in shake flasks and airlift-bioreactors, resulting in reduction of vinasse COD by 34% and viscosity by 21%. Utilization of glycerol and sugars were observed, yielding 202.4 or 222.8g dry fungal biomass of N. intermedia or A. oryzae respectively, per liter of vinasse. Integration of the current process at an existing ethanol facility producing about 100,000m3 of ethanol per year could produce around 200,000-250,000tons of dry fungal biomass (40-45% protein) together with about 8800-12,600m3 extra ethanol (8.8-12.6% of production-rate improvement).

Mild-temperature dilute acid pretreatment for integration of first and second generation ethanol processes

The use of hot-water (100°C) from the 1st generation ethanol plants for mild-temperature lignocellulose pretreatment can possibly cut down the operational (energy) cost of 2nd generation ethanol process, in an integrated model. Dilute-sulfuric and -phosphoric acid pretreatment at 100°C was carried out for wheat bran and whole-stillage fibers. Pretreatment time and acid type influenced the release of sugars from wheat bran, while acid-concentration was found significant for whole-stillage fibers. Pretreatment led up-to 300% improvement in the glucose yield compared to only-enzymatically treated substrates. The pretreated substrates were 191-344% and 115-300% richer in lignin and glucan, respectively. Fermentation using Neurospora intermedia, showed 81% and 91% ethanol yields from wheat bran and stillage-fibers, respectively. Sawdust proved to be a highly recalcitrant substrate for mild-temperature pretreatment with only 22% glucose yield. Both wheat bran and whole-stillage are potential substrates for pretreatment using waste heat from the 1st generation process for 2nd generation ethanol.

Bioethanol Production From Agricultural and Municipal Wastes

Bioethanol, one of the most promising technological advancements of the century, has been widely acclaimed for being produced from diversified origins. Production of bioethanol from food grains (as in Brazil or the United States) is, however, frequently criticized in the food versus fuel debate. Several research studies across the globe, investigating the potential use of various renewable resources (such as waste biomass), have resulted in the emergence of second- and/or third-generation bioethanol processes. This chapter attempts to consolidate various aspects of bioethanol production from solid-waste biomass. Waste biomass of lignocellulosic and starch-based origin, such as municipal solid waste, industrial waste (waste paper or coffee residues), livestock manure, and agricultural waste (wood biomass and agricultural crop residues), are reviewed for their potential to produce ethanol. This chapter describes the feedstock prospects, process technologies, and current research and industrial developments.

Biogas Production: Microbiological Aspects

Anaerobic digestion is a biochemical process where complex organic matter such as carbohydrates, proteins, and lipids degrade in the absence of oxygen and are converted into methane and carbon dioxide by the action of different groups of microorganisms. It is a sustainable waste management technology, which reduces and stabilizes organic wastes, recycles its nutrient and water content, while producing energy. Biogas reduces the demand for fossil fuels, since it can be used for the production of electric power and heat, or converted into vehicle fuel. Currently, methane production via anaerobic digestion is a steadily increasing industry in Europe and all over the world. This chapter focuses on the anaerobic digestion process and the parameters affecting its performance. It also describes briefly the current technologies for anaerobic digestion. Finally, since the degradation of organic material requires a synchronized action of different groups of microorganisms with different metabolic capabilities, this chapter also presents recent developments in molecular biology techniques as valuable tools to obtain in-depth understanding about this complex microbiological system.

Does the second messenger cAMP have a more complex role in controlling filamentous fungal morphology and metabolite production

The effect of second messenger cAMP on the physiological aspects of fungal cells such as pigmentation has been reported previously. However, their actual role in the cellular biochemical cascade that eventually affects the fungal growth morphology, such as mycelial pellet formation, is unclear. This article intends to open up the detailed study on the possible correlative effect of cAMP on the morphological and physiological growth aspects of filamentous fungi, with special emphasis on the industrial metabolite production.

Utilization of wheat straw for fungal phytase production

PurposeWheat straw is an agricultural waste which can be used as a cost effective animal feed. However, high hemicellulose and phytic acid content in wheat straw prevents it as a primary feed choice. Utilization of wheat straw in solid-state fermentation may result in wheat straw valorization and enzyme production. In this study, phytase production in solid-state fermentation of wheat straw using Aspergillus ficuum and valorization of wheat straw were evaluated.MethodsA two-step experimental design procedure was employed for screening and optimization of influencing factors on phytase production. Effects of different nutritional and environmental factors were investigated by one factor at the time method (OFATM). To reach higher amounts of phytase, response surface methodology (RSM) was employed to optimize phytase production as a function of three of the most effective factors.ResultsOptimization of the significant parameters resulted in an increase in the phytase activity from 0.74 ± 0.12 to a maximum of 16.46 ± 0.56 Units per gram dry substrate (U gds−1). The high degree of the fungal phytase activity on wheat straw resulted in the decrease in phytic acid content by 57.4%, as compared to the untreated sample. Scanning electron microscopy (SEM) and FTIR structural analysis showed intensive fungal growth on wheat straw, and partial removal of hemicelluloses, lignin and phytic acid.ConclusionThe study demonstrated the feasibility of wheat straw utilization in solid-state fermentation using Aspergillus ficuum toward the production of phytase and valorization of wheat straw as an animal feed.

Effect of media rheology and bioreactor hydrodynamics on filamentous fungi fermentation of lignocellulosic and starch-based substrates under pseudoplastic flow conditions

The aim of this work was to study how media rheology and bioreactor hydrodynamics would influence fermentation of lignocellulosic and starch-based substrates under pseudoplastic flow conditions. This was investigated using hydrolyzed wheat straw, wheat-based thin stillage and filamentous fungi as inoculum in bubble column, airlift and horizontal hybrid tubular/bubble column (textile bioreactor) bioreactors. The rheological models showed that the consistency index was dependent on biomass growth (R2 0.99) while the flow behavior index depended on biomass growth and suspended solid (R2 0.99). Oxygen transfer rate above 0.356 mmol-O2/L/h was needed for growing fungi with a cube-root growth rate constant of 0.03 g1/3/L1/3/h. At 1.4 VVM aeration the textile bioreactor performed better than others with minimal foaming, yields of 0.22 ± 0.01 g/g and 0.47 ± 0.01 g/g for ethanol and biomass, substrate consumption rate of 0.38 g/L/h. Operating the bioreactors with air-flowrate to cross-sectional area ratio of 8.75 × 10-3 (m3/s/m2) or more led to sustained foaming.