Browsing by Author "Baral, Pratibha"

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    Augmented hydrolysis of acid pretreated sugarcane bagasse by PEG 6000 addition: a case study of Cellic CTec2 with recycling and reuse
    (Springer, 2019-11-08) Baral, Pratibha; Jain, Lavika; Kurmi, Akhilesh Kumar; Kumar, Vinod; Agrawal, Deepti
    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 16 h using Cellic CTec2 by addition of PEG 6000. Addition of this surfactant not only enhanced glucose release by twofold 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 25 mg 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 leads 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. Furthermore, 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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    Comparative assessment of sugarcane bagacillo and bagasse at lab-scale for production of sugars and green chemicals via biochemical platform
    (Springer, 2022-06-08) Baral, Pratibha; Jana, Arijit; Kumar, Vinod; Agrawal, Deepti
    The sugarcane-driven industry can exemplify sustainable waste management by valorizing its lignocellulosic streams and boosting the rural economy by product diversification. In this aspect, bagacillo is a promising yet untapped carbonaceous feedstock, representing fine fraction of sugarcane bagasse (SCB) with low bulk density. It is used either as a filter aid for juice clarification, when added to mud or mixed with bagasse for cogeneration. This study explores bagacillo for the production of sugars and green chemicals using biochemical platform, with SCB as the benchmark. Its NaOH pretreatment preserved > 90 and > 70% glucan and xylan in solid fraction. Fed-batch hydrolysis with Cellic CTec3 at 1-kg scale liberated 167.4 ± 1.87 and 183.53 ± 1.23 g L−1 monomeric sugars in filtrates of bagacillo and SCB, respectively, in 48 h. Its high-ash content reduced glucan conversion yields by 16%, and led to glucan under-estimation in residual biomass during mass balance closure. Irrespective of feedstock type, within 18 h Saccharomyces cerevisiae MTCC 180 and Pachysolen tannophilus MTCC 1077 produced ~ 5% (v/v) ethanol from 1.5L glucose-rich filtrates, with a ~ 18-fold enhancement in biomass accumulation. However, when Bacillus coagulans NCIM 5648 was assessed for high-temperature 2G lactic acid production, the obtained titer from bagacillo-derived hydrolysate (33.6 ± 1.23 g L−1) was lower than SCB (43.38 ± 1.89 g L−1). The present study demonstrated that bagacillo is an equally amenable bioresource as ~ 506 g fermentable sugar was extracted from 1-kg raw biomass and its glucose-rich fraction showed feasibility for microbial transformation to bio-based platform chemicals.
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    Cost reduction approaches for fermentable sugar production from sugarcane bagasse and its impact on techno-economics and the environment
    (Springer, 2021-05-18) Baral, Pratibha; Munagala, Meghana; Shastri, Yogendra; Kumar, Vinod; Agrawal, Deepti
    In an enzymatically driven lignocellulosic biorefinery, pretreatment and hydrolysis modules are the two most significant cost contributors for obtaining high gravity sugar solutions. The present study aimed to reduce the use of alkali and Cellic CTec2 during the bioprocessing of sugarcane bagasse (SCB). Later its impact on the overall process economics and the environment was evaluated. During pretreatment, solid loading of 15% (w/w) and use of 2% (w/v) sodium hydroxide at 121 °C for 30 min emerged as an optimum strategy. It resulted in > 65% delignification of SCB, retaining ≥ 90% and 65% of glucan and xylan fraction, respectively, in the pretreated biomass. Two approaches were evaluated in parallel to minimize the requirement of this commercial cellulase enzyme blend. The first strategy involved its partial replacement with an in-house enzyme cocktail by blending. The second route was performing hydrolysis with reduced loadings of cellulase enzyme blend above its optimum temperature, which gave more promising results. Hydrolysis of 20% alkali pretreated SCB with cellulase enzyme blend dosed at 15 mg protein g−1 glucan led to 84.13 ± 1 and 83.5 ± 2.3% glucan and xylan conversion yields respectively in 48 h at 52.5 °C. The filtrate and wash fraction contained ≥ 165 and ≥ 65 g L−1 sugar monomers representing glucose and xylose. However, in both the fractions > 75%, sugar accounted for glucose. The techno-economic analysis revealed that the sugar production cost from SCB was 1.32 US$/kg, with the optimized bioprocess. Environmental impact study showed that the process contributed to 1.57 kg CO2 eq in terms of climate change.
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    Emerging trends in high-solids enzymatic saccharification of lignocellulosic feedstocks for developing an efficient and industrially deployable sugar platform
    (Taylor and Francis, 2021-09-16) Baral, Pratibha; Kumar, Vinod; Agrawal, Deepti
    For the techno-commercial success of any lignocellulosic biorefinery, the cost-effective production of fermentable sugars for the manufacturing of bio-based products is indispensable. High-solids enzymatic saccharification (HSES) is a straightforward approach to develop an industrially deployable sugar platform. Economic incentives such as reduced capital and operational expenditure along with environmental benefits in the form of reduced effluent discharge makes this strategy more lucrative for exploitation. However, HSES suffers from the drawback of non-linear and disproportionate sugar yields with increased substrate loadings. To overcome this bottleneck, researchers tend to perform HSES at high enzyme loadings. Nonetheless, the production costs of cellulases are one of the key contributors that impair the entire process economics. This review highlights the relentless efforts made globally to attain a high-titer of sugars and their fermentation products by performing efficient HSES at low cellulase loadings. In this context, technical innovations such as advancements in new pretreatment strategies, next-generation cellulase cocktails, additives, accessory enzymes, novel reactor concepts and enzyme recycling studies are especially showcased. This review further covers new insights, learnings and prospects in the area of lignocellulosic bioprocessing.
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    Expeditious production of concentrated glucose-rich hydrolysate from sugarcane bagasse and its fermentation to lactic acid with high productivity
    (Elsevier, 2020-08-22) Baral, Pratibha; Pundir, Anushka; Kumar, Vinod; Kurmi, Akhilesh K.; Agrawal, Deepti
    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 co-generation. 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 25 mg 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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    Salting-out assisted solvent extraction of L (+) lactic acid obtained after fermentation of sugarcane bagasse hydrolysate
    (Elsevier, 2021-04-18) Baral, Pratibha; Pundir, Anushka; Kurmi, Akhilesh; Singh, Raghuvir; Kumar, Vinod; Agrawal, Deepti
    Lactic acid is among the twelve platform chemicals produced from inexpensive and renewable feedstocks such as lignocellulosic biomass. The present study illustrates salting-out assisted solvent extraction of L (+) lactic acid, derived from sugarcane bagasse hydrolysate. Screening studies with various extractants and diluents revealed that a combination of tri-n-butyl phosphate and ethyl acetate yielded the best results and extracted 59.63 ± 1.28% lactic acid from the dilute fermentation broth adjusted to a pH of 1.6 ± 0.2. Various inorganic salts were screened to enhance extraction efficiency further. The addition of 60% (w/v) ammonium sulfate improved the lactic acid extraction by 36.17%. This salt concentration successfully extracted 85.95 ± 0.44% lactic acid to the organic phase under optimized conditions from the fermentation broth at a pH of ~ 2.5 containing 40–100 g L−1 lactic acid. Recovery of > 80% salt is also shown using chilled acetone, which upon reuse showed a nominal decline of 3.3% during extraction. Thus an eco-friendly approach using a green solvent like ethyl acetate with mild operating conditions is demonstrated in the present study.