Genomic comparison of Clostridium species with the potential of utilizing red algal biomass for biobutanol production

Abstract

BackgroundSustainable biofuels, which are widely considered as an attractive alternative to fossil fuels, can be generated by utilizing various biomass from the environment. Marine biomass, such as red algal biomass, is regarded as one potential renewable substrate source for biofuels conversion due to its abundance of fermentable sugars (e.g., galactose). Previous studies focused on the enhancement of biofuels production from different Clostridium species; however, there has been limited investigation into their metabolic pathways, especially on the conversion of biofuels from galactose, via whole genomic comparison and evolutionary analysis.ResultsTwo galactose-utilizing Clostridial strains were examined and identified as Clostridium acetobutylicum strain WA and C. beijerinckii strain WB. Via the genomic sequencing of both strains, the comparison of the whole genome together with the relevant protein prediction of 33 other Clostridium species was established to reveal a clear genome profile based upon various genomic features. Among them, five representative strains, including C. beijerinckii NCIMB14988, C. diolis DSM 15410, C. pasteurianum BC1, strain WA and WB, were further discussed to demonstrate the main differences among their respective metabolic pathways, especially in their carbohydrate metabolism. The metabolic pathways involved in the generation of biofuels and other potential products (e.g., riboflavin) were also reconstructed based on the utilization of marine biomass. Finally, a batch fermentation process was performed to verify the fermentative products from strains WA and WB using 60 g/L of galactose, which is the main hydrolysate from algal biomass. It was observed that strain WA and WB could produce up to 16.98 and 12.47 g/L of biobutanol, together with 21,560 and 10,140 mL/L biohydrogen, respectively.ConclusionsThe determination of the production of various biofuels by both strains WA and WB and their genomic comparisons with other typical Clostridium species on the analysis of various metabolic pathways was presented. Through the identification of their metabolic pathways, which are involved in the conversion of galactose into various potential products, such as biobutanol, the obtained results extend the current insight into the potential capability of utilizing marine red algal biomass and provide a systematic investigation into the relationship between this genus and the generation of sustainable bioenergy.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1044-9) contains supplementary material, which is available to authorized users.

Clostridium sp. as Bio-Catalyst for Fuels and Chemicals Production in a Biorefinery Context

“…acetobutylicum has a high amylase activity, being able to metabolize a variety of carbohydrates, such as starch, glucose, and sucrose [69,70]. Recent studies point out the potential use of C. acetobutylicum for the conversion of algal hydrolysates, algae biomass, and galactose into value-added bioproducts [71]. However, C. acetobutylicum is less effective for complex carbon sources, i.e., lignocellulosic hydrolysates, which may contain toxic substances derived from the dehydration of sugars and aromatics from lignin that are generated during biomass pretreatment [70].…”

“…It is capable of producing chemicals, such as 1,3-propanediol and n-butanol, from renewable raw materials, such as glycerol derived from biodiesel and glucose from hydrolysis of biomass, respectively [71,79]. Ethanol, acetic acid, butyric acid, lactic acid, H 2 , and CO 2 are also among the products of its fermentation.…”

“…In the first step of the methyl group, the possibility of CO assimilation followed by the action of CO desidrogenase generates two protons and two electrons that can be used as inputs to format desidrogenase action on the following reaction. In other words, the WL pathway is capable of sustaining the autotrophic growth of the microorganism only with CO, even without H 2 for electron donation [68,71]. In heterotrophic conditions, alcohols, organic acids, and simple sugars are able to donate electrons to the WL pathway [72].…”

Ultrasonic treatment enhances sludge disintegration and degradation in a photosynthetic bacteria‐bioelectrochemical system

“…The VSS, SS, and SCOD of the sludge were measured according to APHA Standard Methods (Shanmugam, Hari, et al, 2018;Wef, 1998). Protein was measured using the Folin-phenol method, which is a simple accurate method to quantitatively assess wastewater sludge disintegration (Lowry, Rosebrough, Farr, & Randall, 1951;Sun, Zhang, Xin, Shanmugam, & Wu, 2018). The sludge disintegration and degradation characteristics were evaluated by measuring the SCOD, protein, VSS, and SS concentrations (Shanmugam, Sun, Zeng, & Wu, 2018).…”

Bioconversion of organosolv‐treated bamboo into biobutanol integrated with on‐site hydrolytic enzyme production

“…22 This would give a higher hemicellulose and lignin removal efficiency with lower solid yield; however, the presence of acids at high temperature would cause the partial decomposition of hemicellulose sugars and generate inhibitory compounds, such as furfural, hydroxymethyl furfural, and soluble polyphenols from lignin. 23 To overcome these obstacles, different organosolv pretreatment methods, using 70% ethanol in the absence of acid catalysts under mild conditions (35 °C), were investigated (Table 2). Unsurprisingly, the highest sugar concentration (9.4 g L −1 ) was obtained using organosolv pretreatment and H 2 O 2 post-treatment followed by an ethanol wash in each step (No.…”