Biological pretreatment (BP) is a promising approach for treating microalgae and lignocellulosic biomass (LCB) during biofuels production that uses mostly fungal and bacterial strains or their enzymes. Pretreatment with fungi requires long incubation time (weeks to months), whereas, bacterial and enzymatic pretreatments can be completed by only a few hours to days. Nevertheless, fungal pretreatment especially with white-rot fungi (WRF) is predominantly used in BP of biomass for its high efficiency and downstream yields. According to the recent reports, delignification of LCB by WRF may vary between 3% and 72% with a maximum 120% increase in the biofuel yield. Compared to the untreated microalgae biomass, the downstream yields of the respective biofuels were found to be increased by 22–159% after bacterial pretreatment, while enzymatic pretreatment improved as much as 485% of the final yield. Despite the results are promising, exploitation of BP on large scale is still bottlenecked by some technoeconomic hurdles, which need to be overcome through further fundamental and applied researches. This paper presents a comprehensive and in-depth review on BP for LCB and microalgae biomass by focusing on the relevant overviews and perspectives, technological approaches, mechanisms, influencing factors, and recent research progresses. Finally, challenges and future outlooks are discussed in the concluding sections.

Recent advances in biological pretreatment of microalgae and lignocellulosic biomass for biofuel production

Bioconversion of lignocellulosic biomass to xylitol: An overview.

Wine is a complex beverage, comprising thousands of metabolites that are produced through the action of a plethora of yeasts and bacteria during fermentation of grape must. These microbial communities originate in the vineyard and the winery and reflect the influence of several factors including grape variety, geographical location, climate, vineyard spraying, technological practices, processing stage and season (pre-harvest, harvest, post-harvest). Vineyard and winery microbial communities have the potential to participate during fermentation and influence wine flavour and aroma. Therefore, there is an enormous interest in isolating and characterising these communities, particularly non-Saccharomyces yeast species to increase wine flavour diversity, while also exploting regional signature microbial populations to enhance regionality. In this review we describe the role and relevance of the main non-Saccharomyces yeast species found in vineyards and wineries. This includes the latest reports covering the application of these species for winemaking; and the biotechnological characteristics and potential applications of non-Saccharomyces species in other areas. In particular, we focus attention on the species for which molecular and genomic tools and resources are available for study. Copyright © 2016 John Wiley & Sons, Ltd.

Yeasts found in vineyards and wineries.

Improvement of industrially important microbial strains by genome shuffling: Current status and future prospects.

Xylitol is a white crystalline, amorphous sugar alcohol and low-calorie sweetener. Xylitol prevents demineralization of teeth and bones, otitis media infection, respiratory tract infections, inflammation and cancer progression. NADPH generated in xylitol metabolism aid in the treatment of glucose-6-phosphate deficiency-associated hemolytic anemia. Moreover, it has a negligible effect on blood glucose and plasma insulin levels due to its unique metabolism. Its diverse applications in pharmaceuticals, cosmetics, food and polymer industries fueled its market growth and made it one of the top 12 bio-products. Recently, xylitol has also been used as a drug carrier due to its high permeability and non-toxic nature. However, it become a challenge to fulfil the rapidly increasing market demand of xylitol. Xylitol is present in fruit and vegetables, but at very low concentrations, which is not adequate to satisfy the consumer demand. With the passage of time, other methods including chemical catalysis, microbial and enzymatic biotransformation, have also been developed for its large-scale production. Nevertheless, large scale production still suffers from high cost of production. In this review, we summarize some alternative approaches and recent advancements that significantly improve the yield and lower the cost of production.

https://www.mdpi.com/2304-8158/9/11/1592/pdf

Biological and Pharmacological Potential of Xylitol: A Molecular Insight of Unique Metabolism.

Enhanced d-tagatose production by spore surface-displayed l-arabinose isomerase from isolated Lactobacillus brevis PC16 and biotransformation

A new strain producing high yield of d-arabitol was isolated from hyperosmotic environments and the ITS rDNA sequencing analysis revealed it as Zygosaccharomyces rouxii. In addition, using a pH control and repeated-batch fermentation strategy in a 5-L reactor, the maximum yield and the highest volumetric productivity of d-arabitol were 93.48 ± 2.79 g/L and 1.143 g/L h, respectively. Volumetric productivity was successfully improved from 0.86 to 1.143 g/L h, which was increased by 32.9 % after 72 h of fermentation. Z. rouxii JM-C46 has potential to be used for d-arabitol and xylitol production from glucose via d-arabitol route.

Enhanced d-arabitol production by Zygosaccharomyces rouxii JM-C46: isolation of strains and process of repeated-batch fermentation

Enhanced xylitol production: Expression of xylitol dehydrogenase from Gluconobacter oxydans and mixed culture of resting cell.

Microbial and Enzymatic Process for Xylitol Production from D-glucose

The invention relates to a 1,3-propylene glycol genetically engineered bacterium and a method for producing 1,3-propylene glycol by mixing and converting the 1,3-propylene glycol genetically engineered bacterium, and belongs to the field of biotechnology. A PCR (Polymerase Chain Reaction) technology is used for cloning a 1,3-propylene glycol oxidation-reduction enzyme dhaT gene derived from lactobacillus brevis (Lactobacillibrevis CICC6239) so as to construct a genetically engineered strain E.coli-pSE-dhaT which is capable of efficiently and actively expressing the 1,3-propylene glycol oxidation-reduction enzyme (1,3-propanedioldehydrogenase, PDOR). The experiment proves that the enzymatic activity of the 1,3-propylene glycol oxidation-reduction enzyme expressed by the recombinant bacteria is increased by 16 times; the engineered bacterium and the lactobacillus brevis are mixed, stand still and are converted to glycerin, and the conversation rate from the glycerin to the 1,3-propylene glycol can reach 80.6%.

Jingfei Zhu

Papers

Enhanced d-tagatose production by spore surface-displayed l-arabinose isomerase from isolated Lactobacillus brevis PC16 and biotransformation

Enhanced d-arabitol production by Zygosaccharomyces rouxii JM-C46: isolation of strains and process of repeated-batch fermentation

Enhanced xylitol production: Expression of xylitol dehydrogenase from Gluconobacter oxydans and mixed culture of resting cell.

Microbial and Enzymatic Process for Xylitol Production from D-glucose

1,3-propylene glycol genetically engineered bacterium and method for producing 1,3-propylene glycol by converting same