Augmented hydrolysis of acid pretreated sugarcane bagasse by PEG 6000 addition: a case study of Cellic CTec2 with recycling and reuse

Abstract

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.

Cost reduction approaches for fermentable sugar production from sugarcane bagasse and its impact on techno-economics and the environment

“…On the other hand, elevating temperature from 50 to 55C reduced the glucose and xylose release by >20%. A similar observation was made when our group conducted hydrolysis with 7.5% acid pretreated SCB with the same enzyme preparation and raising the temperature from 50 to 55C reduced glucan hydrolysis by ~7% (Baral et al, 2020b). But this time, the high substrate, low enzyme loading, longer duration of hydrolysis and a different pretreatment strategy probably played a pivotal role in severely impeding the saccharification.…”

“…Since the optimum temperature for enzymatic hydrolysis by in-house CCE was 55C whereas for cellulase enzyme blend, it is 50C, therefore, a mid-temperature of 52.5C was chosen for enzyme blending studies (Jain et al, 2019;Baral et al, 2020b). However, before initiating this study, it also became essential to assess the hydrolytic potential of cellulase enzyme blend at 52.5C.…”

Expeditious production of concentrated glucose-rich hydrolysate from sugarcane bagasse and its fermentation to lactic acid with high productivity

“…Saccharification study was carried out at 18% (w/w) substrate loading in a non-buffered medium (pH 4.5) containing PEG 6000 (0.2g/g AISL content) placed in an incubator shaker set at 50C, 180 rpm as described previously (Baral et al, 2020). A two-step substrate feeding strategy (9% + 9%) within a gap of one hour was adopted to mitigate the problem of poor mixing as observed previously (Nalawade et al, 2020).…”

Chestnut Shells as Waste Material for Succinic Acid Production from Actinobacillus succinogenes 130Z

“…Although in recent years a notable decrease in the average chestnut production has been observed due to climate changes and to the invasion of the gall wasp (Dryocosmus kuriphilus Y. ), the Campania region is the major Italian chestnut supplier, with a high availability of waste from processing; therefore, the aim of the present work was to evaluate the growth of A. succinogenes 130Z and the production of succinic acid from ammonia pretreated chestnut shells, hydrolyzed with the Cellic CTec2 commercial enzyme mix that was previously used for the efficient hydrolysis of several lignocellulosic biomasses [15][16][17]. Growth experiments were conducted in bottles and in a controlled 2 L bioreactor to study the performance of A. succinogenes 130Z also on concentrated hydrolysate.…”