Lignocellulosic biomass valorization via bio-photo/electro hybrid catalytic systems

Copolymers as a turning point for large scale polyhydroxyalkanoates applications

Traditional plastics reshaped the society thanks to their brilliant properties and cut-price manufacturing costs. However, their protracted durability and limited recycling threaten the environment. Worthy alternatives seem to be polyhydroxyalkanoates, compostable biopolymers produced by several microbes. The most common 3-hydroxybutyrate homopolymer has limited applications calling for copolymers biosynthesis to enhance material properties. As a growing number of researches assess the discovery of novel comonomers, great endeavors are dedicated as well to copolymers production scale-up, where the choice of the microbial carbon source significantly affects the overall economic feasibility. Diving into novel metabolic pathways, engineered strains, and cutting-edge bioprocess strategies, this review aims to survey up-to-date publications about copolymers production, focusing primarily on precursors origins. Specifically, in the core of the review, copolymers precursors have been divided into three categories based on their economic value: the costliest structurally related ones, the structurally unrelated ones, and finally various low-cost waste streams. The combination of cheap biomasses, efficient pretreatment strategies, and robust microorganisms paths the way towards the development of versatile and circular polymers. Conceived to researchers and industries interested in tackling polyhydroxyalkanoates production, this review explores an angle often underestimated yet of prime importance: if PHAs copolymers offer advanced properties and sustainable end-of-life, the feedstock choice for their upstream becomes a major factor in the development of plastic substitutes.

Response of rumen microorganisms to pH during anaerobic hydrolysis and acidogenesis of lignocellulose biomass

Rumen microorganisms can efficiently degrade lignocellulosic wastes to produce volatile fatty acids (VFAs). pH is a key factor in controlling the type and yield of VFAs by affecting the microorganisms involved in rumen fermentation. However, the effects of different pH on rumen microbial diversity, communities, and mechanisms are unclear. In this study, the hydrolysis and acidogenesis of corn straw and diversity, communities, and mechanisms of rumen microorganisms were explored at different initial pHs. Results showed that the highest hemicellulose, cellulose, and lignin degradation efficiency of corn straw was 55.2 %, 38.3 %, and 7.01 %, respectively, and VFA concentration was 10.2 g/L at pH 7.0. Low pH decreased the bacterial diversity and increased the fungal diversity. Rumen bacteria and fungi had different responses to initial pHs, and the community structure of bacteria and fungi had obviously differences at the genus level. The core genera Succiniclasticum, Treponema, and Neocallimastix relative abundance at initial pH 7.0 samples were significantly higher than that at lower initial pHs, reaching 6.01 %, 1.61 %, and 5.35 %, respectively. The bacterial network was more complex than that of fungi. pH, acetic acid, and propionic acid were the main factors influencing the bacterial and fungal community structure. Low pH inhibited the expression of functional genes related to hydrolysis and acidogenesis, explaining the lower hydrolysis and acidogenesis efficiency. These findings will provide a better understanding for rumen fermentation to produce VFAs.