The liquid-liquid extractive fermentation of L-lactic acid in a novel semi-partition bioreactor (SPB)

Self-Powered Glucose Biosensor Based on Non-Enzymatic Biofuel Cells by Au Nanocluster/Pd Nanocube Heterostructure and Fe3C@C-Fe Single-Atom Catalyst

Self-powered biosensors (SPBs) based on biofuel cells (BFCs) use electrical output as a sensing signal without the need of external power supplies, providing a feasible approach to constructing miniaturized implantable or portable devices. In this work, a novel nanozyme of gold nanoclusters/palladium nanocubes (AuNCs/PdNCs) heterostructure is successfully fabricated to develop an innovatively self-powered and non-enzymatic glucose sensing system. The AuNCs/PdNCs with glucose oxidase (GOD)-like activity exhibits superior electrocatalytic and non-enzymatic sensing performance toward glucose. The non-enzymatic BFCs-based SPBs system, established on the AuNCs/PdNCs (anodic catalyst) and single atomic Fe sites coupled with carbon-encapsulated Fe3C crystals (Fe3C@C-Fe SACs as a cathodic catalyst) platform, exhibits an exceptional sensitivity to glucose with 0.151 µW cm-2 mm-1 (3.4 times higher than the PdNCs), outstanding selectivity and robust stability. The outstanding performance of the BFCs-based SPBs system can be attributed to the synergistic cooperation between the PdNCs and AuNCs.

Bioprocesses for lactic acid production from organic wastes toward industrialization-a critical review

Lactic acid (LA) is a crucial chemical which has been widely used for industrial application. Microbial fermentation is the dominant pathway for LA production and has been regarded as the promising technology. In recent years, many studies on LA production from various organic wastes have been published, which provided alternative ways to reduce the LA production cost, and further recycle organic wastes. However, few researchers focused on industrial application of this technology due to the knowledge gap and some uncertainties. In this review, the recent advances, basic knowledge and limitations of LA fermentation from organic wastes are discussed, the challenges and suitable envisaged solutions for enhancing LA yield and productivity are provided to realize industrial application of this technology, and also some perspectives are given to further valorize the LA fermentation processes from organic wastes. This review can be a useful guidance for industrial LA production from organic wastes on a sustainable view.

Metabolic Engineering and Process Intensification for Muconic Acid Production Using Saccharomyces cerevisiae

The efficient production of biobased organic acids is crucial to move to a more sustainable and eco-friendly economy, where muconic acid is gaining interest as a versatile platform chemical to produce industrial building blocks, including adipic acid and terephthalic acid. In this study, a Saccharomyces cerevisiae platform strain able to convert glucose and xylose into cis,cis-muconic acid was further engineered to eliminate C2 dependency, improve muconic acid tolerance, enhance production and growth performance, and substantially reduce the side production of the intermediate protocatechuic acid. This was achieved by reintroducing the PDC5 gene and overexpression of QDR3 genes. The improved strain was integrated in low-pH fed-batch fermentations at bioreactor scale with integrated in situ product recovery. By adding a biocompatible organic phase consisting of CYTOP 503 and canola oil to the process, a continuous extraction of muconic acid was achieved, resulting in significant alleviation of product inhibition. Through this, the muconic acid titer and peak productivity were improved by 300% and 185%, respectively, reaching 9.3 g/L and 0.100 g/L/h in the in situ product recovery process as compared to 3.1 g/L and 0.054 g/L/h in the control process without ISPR.

Simultaneous fermentation and enzymatic biocatalysis-a useful process option?

Biotransformation with enzymes and de novo syntheses with whole-cell biocatalysts each have specific advantages. These can be combined to achieve processes with optimal performance. A recent approach is to perform bioconversion processes and enzymatic catalysis simultaneously in one-pot. This is a well-established process in the biorefinery, where starchy or cellulosic material is degraded enzymatically and simultaneously used as substrate for microbial cultivations. This procedure leads to a number of advantages like saving in time but also in the needed equipment (e.g., reaction vessels). In addition, the inhibition or side-reaction of high sugar concentrations can be overcome by combining the processes. These benefits of coupling microbial conversion and enzymatic biotransformation can also be transferred to other processes for example in the sector of biofuel production or in the food industry. However, finding a compromise between the different requirements of the two processes is challenging in some cases. This article summarises the latest developments and process variations.

A review on the upstream production and downstream purification of mannosylerythritol lipids

Biosurfactants are natural compounds with remarkable surface-active properties that may offer an eco-friendly alternative to conventional surfactants. Among them, mannosylerythritol lipids (MELs) stand out as an intriguing example of a glycolipid biosurfactant. MELs have been used in a variety of sectors for various applications, and are currently commercially produced. Industrially, they are used in the pharmaceutical, cosmetic, food, and agricultural industries, based on their ability to reduce surface tension and enhance emulsification. However, despite their utility, their production is comparatively limited industrially. From a bioprocessing standpoint, two areas of interest to improve the production process are upstream production and downstream (separation and purification) product recovery. The former has seen a significant amount of research, with researchers investigating several production factors: the microbial species or strain employed, the producing media composition, and the production strategy implemented. Improvement and optimization of these are key to scale-up the production of MELs. On the other hand, the latter has seen comparatively limited work presented in the literature. For the most part traditional separation techniques have been employed. This systematic review presents the production and purification methodologies used by researchers by comprehensively analyzing the current state-of-the-art with regards the production, separation, and purification of MELs. By doing so, the review presents different possible approaches, and highlights some potential areas for future work by identifying opportunities for the commercialization of MELs.

Towards industrial biological hydrogen production: a review

Increased production of renewable energy sources is becoming increasingly needed. Amidst other strategies, one promising technology that could help achieve this goal is biological hydrogen production. This technology uses micro-organisms to convert organic matter into hydrogen gas, a clean and versatile fuel that can be used in a wide range of applications. While biohydrogen production is in its early stages, several challenges must be addressed for biological hydrogen production to become a viable commercial solution. From an experimental perspective, the need to improve the efficiency of hydrogen production, the optimization strategy of the microbial consortia, and the reduction in costs associated with the process is still required. From a scale-up perspective, novel strategies (such as modelling and experimental validation) need to be discussed to facilitate this hydrogen production process. Hence, this review considers hydrogen production, not within the framework of a particular production method or technique, but rather outlines the work (bioreactor modes and configurations, modelling, and techno-economic and life cycle assessment) that has been done in the field as a whole. This type of analysis allows for the abstraction of the biohydrogen production technology industrially, giving insights into novel applications, cross-pollination of separate lines of inquiry, and giving a reference point for researchers and industrial developers in the field of biohydrogen production.

Development of an ultrasound-assisted pre-treatment strategy for the extraction of D-Limonene toward the production of bioethanol from citrus peel waste (CPW)

Citrus is one of the world's most abundant fruits containing vitamins, pigments, and fragrances, making it vital for several industries. However, these fruits contain about 45-50% residues (peels), which often end up as waste and can be harmful to the environment if not properly treated. Bioethanol production from citrus peel waste offers a potential solution to this problem. Hence, this study explores the potential of using ultrasound-assisted pre-treatment method as a novel strategy to extract D-Limonene (essential oil in the residue), and further demonstrates bioethanol production. This was done by investigating ultrasonication's optimal effect on pre-treatment of the citrus residue, followed by bioethanol production. The results show that, optimum values for D-Limonene extraction were obtained at a temperature of 14.6 °C and an ultrasound intensity of 25.81 W/cm2 with a validation yield of 134 ± 4.24 mg/100 g dry CPW. With optimal ultrasonic parameters, the study went further to demonstrate the effect of the essential oil on bioethanol production which is hindered by the oils present. Key findings show better bioethanol yield once the essential oil was extracted (treated) from the citrus waste as opposed to it not extracted (untreated), with a 66 and a 29% increase when comparing simultaneous saccharification and fermentation (SSF) and sequential hydrolysis and fermentation (SHF) respectively. Based on this result, ultrasound-assisted extraction as a pretreatment method was found suitable for bioethanol production from citrus residue and could be utilized as a biorefinery pre-treatment approach to scale bioethanol production.