scholarly journals A comparative evaluation of fermentable sugars production from oxidative, alkaline, alkaline peroxide oxidation, dilute acid, and molten hydrate salt pretreatments of corn cob biomass

AIMS Energy ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 15-28
Author(s):  
Augustine O. Ayeni ◽  
◽  
Michael O. Daramola ◽  
Oluranti Agboola ◽  
Ayodeji A. Ayoola ◽  
...  
2021 ◽  
Vol 38 (1) ◽  
pp. 81-89
Author(s):  
Augustine Omoniyi Ayeni ◽  
Oluranti Agboola ◽  
Michael Olawale Daramola ◽  
Bianca Grabner ◽  
Babalola Aisosa Oni ◽  
...  

2021 ◽  
Vol 8 (1) ◽  
pp. 1947444
Author(s):  
Olayile Ejekwu ◽  
Augustine Omoniyi Ayeni ◽  
Olawumi Sadare ◽  
Michael Olawale Daramola
Keyword(s):  
Corn Cob ◽  

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Cathleen Kmezik ◽  
Cyrielle Bonzom ◽  
Lisbeth Olsson ◽  
Scott Mazurkewich ◽  
Johan Larsbrink

Abstract Background Plant biomass is an abundant and renewable carbon source that is recalcitrant towards both chemical and biochemical degradation. Xylan is the second most abundant polysaccharide in biomass after cellulose, and it possesses a variety of carbohydrate substitutions and non-carbohydrate decorations which can impede enzymatic degradation by glycoside hydrolases. Carbohydrate esterases are able to cleave the ester-linked decorations and thereby improve the accessibility of the xylan backbone to glycoside hydrolases, thus improving the degradation process. Enzymes comprising multiple catalytic glycoside hydrolase domains on the same polypeptide have previously been shown to exhibit intramolecular synergism during degradation of biomass. Similarly, natively fused carbohydrate esterase domains are encoded by certain bacteria, but whether these enzymes can result in similar synergistic boosts in biomass degradation has not previously been evaluated. Results Two carbohydrate esterases with similar architectures, each comprising two distinct physically linked catalytic domains from families 1 (CE1) and 6 (CE6), were selected from xylan-targeting polysaccharide utilization loci (PULs) encoded by the Bacteroidetes species Bacteroides ovatus and Flavobacterium johnsoniae. The full-length enzymes as well as the individual catalytic domains showed activity on a range of synthetic model substrates, corn cob biomass, and Japanese beechwood biomass, with predominant acetyl esterase activity for the N-terminal CE6 domains and feruloyl esterase activity for the C-terminal CE1 domains. Moreover, several of the enzyme constructs were able to substantially boost the performance of a commercially available xylanase on corn cob biomass (close to twofold) and Japanese beechwood biomass (up to 20-fold). Interestingly, a significant improvement in xylanase biomass degradation was observed following addition of the full-length multidomain enzyme from B. ovatus versus the addition of its two separated single domains, indicating an intramolecular synergy between the esterase domains. Despite high sequence similarities between the esterase domains from B. ovatus and F. johnsoniae, their addition to the xylanolytic reaction led to different degradation patterns. Conclusion We demonstrated that multidomain carbohydrate esterases, targeting the non-carbohydrate decorations on different xylan polysaccharides, can considerably facilitate glycoside hydrolase-mediated hydrolysis of xylan and xylan-rich biomass. Moreover, we demonstrated for the first time a synergistic effect between the two fused catalytic domains of a multidomain carbohydrate esterase.


1978 ◽  
Vol 35 (4) ◽  
pp. 397-402 ◽  
Author(s):  
Alan W. White ◽  
Lucie Maranda

Paralytic toxins were examined quantitatively in a culture of Gonyaulax excavata and in shellfish by the standard mouse bioassay and by an alkaline peroxide oxidation–fluorometric assay for saxitoxin (STX). The dinoflagellate probably contains at least three toxins, including STX, which represents 3–20% of the total toxin load. During growth in culture the toxin content per cell decreased progressively; however, relative amounts of the three toxins remained roughly similar. In toxic shellfish from nature (Mya arenaria, Mytilus edulis, Modiolus modiolus) and in shellfish fed G. excavata under controlled conditions the relative amounts of toxins differed from those in G. excavata, suggesting toxin interconversions and interference with the chemical assay by toxins other than STX. The consistency in the relationships between bioassay and chemical assay results for clam samples was fair, although the chemical assay measured from 16 to 48% of the bioassay. The chemical assay is questionable as an indicator of total toxin content, and until further data are accumulated the mouse bioassay method is considered more reliable for measuring paralytic, G. excavata toxins in shellfish. Key words: Gonyaulax excavata, dinoflagellate toxins, paralytic shellfish poisoning, saxitoxin, toxin measurement


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