Substrate-related factors and kinetic studies of Carbohydrate-Rich food wastes on enzymatic saccharification

Energy and carbon-efficient one-pot bioprocessing for upcycling non-sterile food waste into high-yield 2,3-butanediol production

Food waste is a significant global issue whose unsatisfactory management leads to greenhouse gas emissions and loss of resources. Repurposing food waste from landfills to sustainable bioprocessing supports the circular bioeconomy. This study explores converting non-sterile food waste into 2,3-butanediol (2,3-BDO), a versatile chemical, using a one-pot bioprocessing (OPB) method which integrates enzymatic saccharification and fermentation to improve efficiency and reduce costs. Optimizing solid-to-liquid ratios (20 % w/v), inoculum sizes (10 % vol.) of Klebsiella pneumoniae strain PM2, and fermentation strategies (batch and fed-batch) maximizes yields. Fed-batch cultivation with constant feeding at 1.5 mL/h for 42 h reached a maximum titer of 78.4 g/L (85.5 % of the theoretical yield), a 33.5 % improvement over the benchmark separate hydrolysis and fermentation (SHF) process. Compositional variability of food waste (glucose r = 0.99) also greatly impacted 2,3-BDO production. Energy and carbon footprint analyses reveal that food waste biorefineries offer a significant reduction in energy consumption with a -0.86 kWh/kg-FW and carbon benefits of 1.41 kgCO2-eq./kg-FW over traditional disposal methods, reducing greenhouse gas emissions by 97.3 % compared to sugar biorefineries and promoting a circular economy. The findings underscore the potential of food waste as a sustainable feedstock for bioproducts, advocating for policy support to advance bioconversion technologies.

Impact of co-substrate molecular weight on methane production potential, microbial community dynamics, and metabolic pathways in waste activated sludge anaerobic co-digestion

Proteins and carbohydrates are important organics in waste activated sludge, and greatly affect methane production and microbial community composition in anaerobic digestion systems. Here, a series of co-substrates with different molecular weight were applied to investigate the interactions between microbial dynamics and the molecular weight of co-substrates. Biochemical methane production assays conducted in batch co-digesters showed that feeding high molecular weight protein and carbohydrate substrates resulted in higher methane yield and production rates. Moreover, high-molecular weight co-substrates increased the microbial diversity, enriched specific microbes including Longilinea, Anaerolineaceae, Syner-01, Methanothrix, promoted acidogenic and acetoclastic methanogenic pathways. Low-molecular weight co-substrates favored the growth of JGI-0000079-D21, Armatimonadota, Methanosarcina, Methanolinea, and improved hydrogenotrophic methanogenic pathway. Besides, Methanoregulaceae and Methanolinea were indicators of methane yield. This study firstly revealed the complex interactions between co-substrate molecular weight and microbial communities, and demonstrated the feasibility of adjusting co-substrate molecular weight to improve methane production process.

Sustainability in Membrane Technology: Membrane Recycling and Fabrication Using Recycled Waste

Membrane technology has shown a promising role in combating water scarcity, a globally faced challenge. However, the disposal of end-of-life membrane modules is problematic as the current practices include incineration and landfills as their final fate. In addition, the increase in population and lifestyle advancement have significantly enhanced waste generation, thus overwhelming landfills and exacerbating environmental repercussions and resource scarcity. These practices are neither economically nor environmentally sustainable. Recycling membranes and utilizing recycled material for their manufacturing is seen as a potential approach to address the aforementioned challenges. Depending on physiochemical conditions, the end-of-life membrane could be reutilized for similar, upgraded, and downgraded operations, thus extending the membrane lifespan while mitigating the environmental impact that occurred due to their disposal and new membrane preparation for similar purposes. Likewise, using recycled waste such as polystyrene, polyethylene terephthalate, polyvinyl chloride, tire rubber, keratin, and cellulose and their derivates for fabricating the membranes can significantly enhance environmental sustainability. This study advocates for and supports the integration of sustainability concepts into membrane technology by presenting the research carried out in this area and rigorously assessing the achieved progress. The membranes' recycling and their fabrication utilizing recycled waste materials are of special interest in this work. Furthermore, this study offers guidance for future research endeavors aimed at promoting environmental sustainability.