Several efforts have been made during the last three decades to develop successful lignocellulose-based technologies for the production of fuels and chemicals. However, such technologies still seemed to be emerging, because of the high technical risks involved and huge capital investments. This paper describes a holistic approach toward utilization of sugar cane bagasse as lignocellulosic feedstock into fuel (ethanol), chemical (furfural), and energy (electricity), using a biorefinery approach instead of co-generation. The proposed scheme could be integrated with existing sugar or paper mills, where the availability of biomass feedstock is in abundance. Fermentable sugar components (xylose and glucose) from sugar cane bagasse have been extracted employing acid hydrolysis and enzymatic saccharification. Recovery and reuse of saccharifying enzyme was a major process advantage. The pentose fraction was efficiently utilized for yeast biomass generation and furfural production. High-temperature fermentation of a hexose stream by thermophilic yeast Kluyveromyces sp. IIPE453 (MTCC 5314) with cell recycle produced ethanol with an overall yield of 88% ± 0.05% and a productivity of 0.76 ± 0.02 g/L h–1. A complete material balance on two consecutive process cycles, each starting with 1 kg of feedstock, resulted in an overall yield of 366 mL of ethanol, 149 g of furfural, and 0.30 kW of electricity.

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Sugarcane bagasse (SCB) is anticipated to emerge as a potential threat to waste management in India on account of cheap surplus energy options and lower incentives through its cogeneration. Through biotechnological intervention, the efficient utilization of SCB is seen as an opportunity. The present study aimed towards expeditious production of concentrated glucose-rich hydrolysate from SCB. Alkali pretreated biomass was chosen for hydrolysis with a new generation cellulase cocktail, Cellic CTec2 dosed at 25mg g -1 glucan content. A two-step (9% + 9%) substrate feeding strategy was adopted with a gap of an hour, and saccharification was terminated in three different ways. Irrespective of the methods employed for termination, ~84.5% cellulose was hydrolyzed releasing ≥100 g L -1 glucose from 18% biomass. Direct use of glucose-rich filtrates yielded 69.2 ± 2.5 g L -1 of L (+) lactic acid (LA) using thermophilic Bacillus coagulans NCIM 5648. The best-attained glucose and LA productivities during separate hydrolysis and fermentation (SHF) in the present study were 5.27 and 2.88 g L -1 h -1 , respectively. A green and sustainable process is demonstrated for the production of industrially relevant sugars from SCB at high productivity and its valorization to bio-based LA.

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In an integrated lignocellulosic biorefinery, the cost associated with the "cellulases" and "longer duration of cellulose hydrolysis" represents the two most important bottlenecks. Thus to overcome these barriers, the present study aimed towards augmented hydrolysis of acid pretreated sugarcane bagasse within a short span of 16h using Cellic CTec2 by addition of PEG 6000. Addition of this surfactant not only enhanced glucose release by two fold within stipulated time, but aided in recovery of Cellic CTec2 which was further recycled and reused for second round of saccharification. During first round of hydrolysis, when Cellic CTec2 was loaded at 25mg protein /g cellulose content, it resulted in 76.24± 2.18% saccharification with a protein recovery of 58.4 ± 1.09%. Filtration through 50KDa PES membrane retained ~89% protein in 4.5 fold concentrated form and lead to simultaneous fractionation of ~70% glucose in the permeate. Later, the saccharification potential of recycled Cellic CTec2 was assessed for the second round of saccharification using two different approaches. Unfortified enzyme effectively hydrolysed 67% cellulose whereas 72% glucose release was observed with Cellic CTec2 fortified with 25% fresh protein top-up. Incorporating the use of the recycled enzyme in two-stage hydrolysis could effectively reduce the Cellic CTec2 loading from 25 to 16.8 mg protein/g cellulose. Further, 80% ethanol conversion efficiencies were achieved when glucose-rich permeate obtained after the first and second rounds of saccharification were evaluated using Saccharomyces cerevisiae MTCC 180.

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