Cell-based high-throughput screening of polysaccharide biosynthesis hosts

Microbial polysaccharides biosynthesis and their regulatory strategies

Microbial polysaccharides hold significant potential for various applications, including food, cosmetics, petroleum, and pharmaceuticals. A deeper understanding of their biosynthetic pathways and regulatory strategies is crucial for enhancing production efficiency and reducing associated costs. To summarize synthetic biological modification strategies for microbial polysaccharides from a hierarchical perspective, this review classifies these polymers into three categories based on the depths of carried out research regarding their biosynthetic pathways and regulatory strategies, i.e., (1) microbial polysaccharides with well-elucidated biosynthetic pathways, (2) microbial polysaccharides with well-elucidated precursor sugar biosynthetic pathways but synthase-encoding genes incompletely understood, and (3) those whose biosynthesis depends on a single synthetic enzyme. We systematically summarize the biosynthetic pathways of these three categories and provide insights into yield-improvement strategies. This review aims to serve as a valuable reference for metabolic regulation of microbial polysaccharides and to facilitate future advances in their production.

Harnessing the polysaccharide production potential to optimize and expand the application of probiotics

Certain probiotic microorganisms can synthesize important bioproducts, including polysaccharides as components of cellular structure or extracellular matrix. Probiotic-derived polysaccharides have been widely applied in food, pharmaceutical, and medical fields due to their excellent properties and biological activities. The development of polysaccharide production potential has become a driving force for facilitating biotechnological applications of probiotics. Based on technical advances in synthetic biology, significant progress has recently been made in engineering probiotics with efficient biosynthesis of polysaccharides. Herein, this review summarizes probiotics chassis and genetic tools used for polysaccharide production. Then, probiotic polysaccharides and relevant biosynthesis mechanisms are also clearly described. Next, we introduce strategies for preparing high-yield, controllable molecular weight or non-native polysaccharides by adjusting metabolic pathways and integrating expression elements in probiotics. Finally, some prospective and well-established contributions of exogenous and in situ polysaccharides in probiotics' stability, bioactivity, and therapeutic effects are presented. Our viewpoints on advancing the efficient biomanufacturing of valuable biopolymers in probiotics and engineering probiotics with customized features are provided to exploit probiotics' industrial and biomedical applications.

Exopolysaccharide production by salt-tolerant bacteria: Recent advances, current challenges, and future prospects

Natural biopolymers derived from exopolysaccharides (EPSs) are considered eco-friendly and sustainable alternatives to available traditional synthetic counterparts. Salt-tolerant bacteria inhabiting harsh ecological niches have evolved a number of unique adaptation strategies allowing them to maintain cellular integrity and assuring their long-term survival; among these, producing EPSs can be adopted as an effective strategy to thrive under high-salt conditions. A great diversity of EPSs from salt-tolerant bacteria have attracted widespread attention recently. Because of factors such as their unique structural, physicochemical, and functional characteristics, EPSs are commercially valuable for the global market and their application potential in various sectors is promising. However, large-scale production and industrial development of these biopolymers are hindered by their low yields and high costs. Consequently, the research progress and future prospects of salt-tolerant bacterial EPSs must be systematically reviewed to further promote their application and commercialization. In this review, the structure and properties of EPSs produced by a variety of salt-tolerant bacterial strains isolated from different sources are summarized. Further, feasible strategies for solving production bottlenecks are discussed, which provides a scientific basis and direct reference for more scientific and rational EPS development.

Marine Microbial Polysaccharides: An Untapped Resource for Biotechnological Applications

As the largest habitat on Earth, the marine environment harbors various microorganisms of biotechnological potential. Indeed, microbial compounds, especially polysaccharides from marine species, have been attracting much attention for their applications within the medical, pharmaceutical, food, and other industries, with such interest largely stemming from the extensive structural and functional diversity displayed by these natural polymers. At the same time, the extreme conditions within the aquatic ecosystem (e.g., temperature, pH, salinity) may not only induce microorganisms to develop a unique metabolism but may also increase the likelihood of isolating novel polysaccharides with previously unreported characteristics. However, despite their potential, only a few microbial polysaccharides have actually reached the market, with even fewer being of marine origin. Through a synthesis of relevant literature, this review seeks to provide an overview of marine microbial polysaccharides, including their unique characteristics. In particular, their suitability for specific biotechnological applications and recent progress made will be highlighted before discussing the challenges that currently limit their study as well as their potential for wider applications. It is expected that this review will help to guide future research in the field of microbial polysaccharides, especially those of marine origin.