Indra Neel Pulidindi

Single step production of bioethanol from the seaweed Ulva rigida using sonication

Ulva rigida, a common green seaweed, was used as a feedstock for the production of bioethanol in a simultaneous saccharification and fermentation (SSF) process carried out under sonication. Sonication provided a faster way for the simultaneous release of glucose from Ulva rigida and its conversion into bioethanol. Within 3 h, 196 ± 2.5 mg glucose per gram of dry weight of biomass and 333.3 ± 4.7 mg bioethanol per gram of glucose were produced in the SSF process under sonication. In addition to being fast, the process was devoid of any chemical pretreatment and involves only a single stage of sonication for the release of glucose from algae by the action of enzymes and also for the simultaneous fermentation of glucose to ethanol using Saccharomyces cerevisiae.

Levulinic acid production from Cicer arietinum, cotton, Pinus radiata and sugarcane bagasse

Levulinic acid is a key platform chemical. Even gasoline range chemicals could be produced from levulinic acid making it a strategically significant compound. Producing levulinic acid from biomass is attractive from economic as well as environmental aspects. An acid catalyzed hydrothermal process for converting biomass to levulinic acid is reported. The effect of biomass type, acid (HCl) concentration, and reaction temperature of hydrothermal treatment on the conversion of biomass and yield of levulinic acid were studied. Widely available cellulosic biomass and agricultural wastes, namely, Cicer arietinum, cotton, Pinus radiata and sugarcane bagasse were successfully converted to levulinic acid. Although HPCL analysis could not be performed, qualitative and quantitative analysis of levulinic acid was conducted using 13C and 1H NMR spectroscopy. Under optimal reaction conditions (423 K, 1 M HCl, 2 h) the yields of levulinic acid obtained from Cicer arietinum, cotton, Pinus radiata and sugarcane bagasse were 32.6, 44.0, 19.0 and 36.5 wt%.

Continuous flow through a microwave oven for the large-scale production of biodiesel from waste cooking oil

This report presents a method for producing large quantities of biodiesel from waste cooking oil (WCO). Preliminary studies on optimization of the WCO transesterification process in a continuous-flow microwave reactor are carried out using commercial SrO as a catalyst. The SrO catalyst can be separated and reused for five reaction cycles without loss in activity. Challenges like mass flow and pressure drop constraints need to be surmounted. SrO nanoparticles deposited on millimeter-sized (3-6mm) silica beads (41wt% SrO/SiO2) are prepared and evaluated as a substitute for the SrO catalyst. A WCO conversion value to biodiesel as high as 99.2wt% was achieved with the reactor packed with 15g of 41wt% SrO/SiO2 catalyst in 8.2min with 820mL of feed. Excellent performance of the fixed-bed catalyst without loss in activity for a lifetime of 24.6min converting a feed of 2.46L to FAME was observed.

Direct production of glucose from glycogen under microwave irradiation

The production of fermentable sugars from renewable sources is a challenge. An attempt was made to exploit glycogen as a potential feedstock for the production of glucose. The microwave-assisted acidic hydrolysis was applied for glycogen decomposition for the first time. The optimal conditions for the hydrolysis reaction (yield of glucose – 62 wt.%) were identified: microwave irradiation time – 10 min and concentration of acid – 1 M HCl. Microwave irradiation has dramatically reduced the reaction time from more than 6 h (at 80 °C under an oil bath) to 10 min. 13C NMR spectroscopy was employed to monitor the progress of the hydrolysis reaction. HPLC analysis was employed to evaluate the yield of glucose. Thus, the viability of the use of glycogen as an economically and environmentally benign precursor to the production of glucose has been demonstrated.

Sonochemical synthesis of HSiW/graphene catalysts for enhanced biomass hydrolysis

Hydrolysis of biomass for the production of glucose was studied. Silicotungstic acid (HSiW) was deposited on graphene by an ultrasound-assisted procedure. The catalyst (HSiW/G) was characterized using a variety of physico-chemical methods. Homogeneous distribution of HSiW on the surface of graphene was demonstrated. The hydrolysis of glycogen was performed with a HSiW/G catalyst by hydrothermal treatment. The yield of glucose (66 wt%) obtained was about 8 times higher than that obtained with the same amount of bare HSiW. Stability of the HSiW/graphene even after 3 repeated uses was confirmed. The mechanism of the enhancement of catalytic activity was discussed in terms of a special interaction between the graphene support and HSiW and also the appearance of hydrophobic cavities on the surface of graphene. The formation of these cavities facilitates the anchoring of glycogen to the catalyst surface and promotes the attack of protons that leads to selective, rapid, and efficient hydrolysis.

Synergistic catalytic effect of the ZnBr2–HCl system for levulinic acid production using microwave irradiation

A catalytic process for the selective conversion of carbohydrates to levulinic acid is developed. A synergy in the catalytic action is observed when a combination of ZnBr2 and HCl was used as the catalyst which is attributed to the in situ generation of HBr. Carbohydrates, namely, glucose, molasses and sucrose, were employed as feedstock for levulinic acid production. Microwave irradiation of glucose either in the presence of HCl alone or both HCl and ZnBr2 as catalysts yielded the formation of levulinic acid. But the conversion of glucose to levulinic acid was much faster (only 6 min) when both HCl and ZnBr2 were employed together. The effect of the reaction parameters like, the time of irradiation, % power, and amount of substrate and catalyst on the yield of levulinic acid were studied. The reaction products in each case were analysed using 1H and 13C NMR. The yield of levulinic acid was estimated using HPLC. The maximum yield of levulinic acid obtained from glucose was 53 wt%.

Production of 1,3-propanediol from glycerol via fermentation by Saccharomyces cerevisiae

The demand for 1,3-propanediol-based polymers is constantly increasing, necessitating an increase in 1,3-propanediol production. While the processes for the chemical and bacterial synthesis of 1,3-propanediol are well-known, we report for the first time the possibility of glycerol conversion to 1,3-propanediol by a fungal strain. The synthesis of 1,3-propanediol by biological means is extremely lucrative, and to the best of our knowledge, this is the first study focusing on the development of an optimized process for the production of the value-added chemical 1,3-propanediol from what can be considered as industrial waste, glycerol, via fermentation using instant bakers yeast (Saccharomyces cerevisiae). Various glycerol fermentation conditions (aerobic, semi-aerobic, and anaerobic) were tested at different reaction temperatures (25, 30, and 37 °C). Under optimal reaction conditions (anaerobic fermentation at 25 °C), 42.3 wt% 1,3-propanediol yield was achieved with 93.6 wt% glycerol conversion.

Marine integrated culture of carbohydrate rich Ulva rigida for enhanced production of bioethanol

Macro algal seaweeds are a promising feedstock for biofuels production. Yet, their relatively low fermentable carbohydrate content and the inefficient methods used for their conversion hamper their utilization. The optimized production of Ulva rigida co-cultured with fed-fish in an offshore mariculture (fish cages) system is reported. Enhanced production of biomass with elevated content of desired carbohydrates is achieved. The farmed biomass was further converted to bioethanol by a one-step sonication assisted SSF process. An ethanol yield of 16 wt% (based on the dry weight of algae) is obtained.

Employing Novel Techniques (Microwave and Sonochemistry) in the Synthesis of Biodiesel and Bioethanol

Energy crisis and environmental deterioration are the twin problems facing the mankind. Alternate energy sources, especially, biofuels (biodiesel and bioethanol) produced from renewable sources like biomass would alleviate the problem to some extent. Fast and demand based production of biofuels is the need of the hour. Transesterification is the crucial chemical reaction for biodeisel production. Likewise, biomass pretreatment, hydrolysis of carbohydrates and fermentation of sugars are vital in bioethanol production. Interestingly, both the unconventional techniques, sonication and microwave irradiation were found to be extremely useful in accelerating the afore mentioned reactions holding a promise for making sustainable biorefinery possible. The present chapter fully covered the work on carrying out the biodiesel synthesis employing Sonochemistry , however, the use of MW radiation for the synthesis of biodiesel was limited to solid base catalysts. The second part of the chapter was devoted to the use of MW and sonochemistry for the synthesis of bioethanol.

Design of a selective solid acid catalyst for the optimization of glucose production from Oryza sativa straw

A selective, green and fast method for the production of glucose from rice (Oryza sativa) straw is demonstrated. Aq. ammonia based pretreatment techniques played a crucial role in the removal of lignin and xylan from rice straw which in-turn accelerated glucan hydrolysis and improved the selectivity of glucose production. The cellulose isolated from rice straw is further hydrolyzed to glucose using a solid acid catalyst (activated carbon supported phosphotungstic acid, ∼40 wt% HPW/AC). Microwave irradiation of cellulose from rice straw for a short duration of 5 min at 100 °C yielded 11.2 wt% glucose relative to 8 wt% glucose produced from a hydrothermal hydrolysis process (3 h, 150 °C) with a substrate to catalyst wt/wt ratio of 1. Thus an effective biomass pretreatment (aq. ammonia–dil. H2SO4) method and an accelerated selective biomass hydrolysis process is developed.