Enhanced polyhydroxybutyrate production from acid whey through determination of process and metabolic limiting factors

The green revolution of food waste upcycling to produce polyhydroxyalkanoates

This review emphasizes the urgent need for food waste upcycling as a response to the mounting global food waste crisis. Focusing on polyhydroxyalkanoates (PHAs) as an alternative to traditional plastics, it examines the potential of various food wastes as feedstock for microbial fermentation and PHA production. The upcycling of food waste including cheese whey, waste cooking oil, coffee waste, and animal fat is an innovative practice for food waste management. This approach not only mitigates environmental impacts but also contributes to sustainable development and economic growth. Downstream processing techniques for PHAs are discussed, highlighting their role in obtaining high-quality materials. The study also addresses sustainability considerations, emphasizing biodegradability and recycling, while acknowledging the challenges associated with this path.

Phenotype-genotype mapping reveals the betaine-triggered L-arginine overproduction mechanism in Escherichia coli

The production phenotype improvement of industrial microbes is extremely needed and challenging. Environmental factors optimization provides insightful ideas to trigger the superior production phenotype by activating potential genetic determiners. Here, phenotype-genotype mapping was used to dissect the betaine-triggered L-arginine overproduction mechanism and mine beneficial genes for further improving production phenotype. The comparative transcriptomic analysis revealed a novel role for betaine in modulating global gene transcription. Guided by this finding, 4 novel genes (cynX, cynT, pyrB, and rhaB) for L-arginine biosynthesis were identified via reverse engineering. Moreover, the rhaB deletion was demonstrated as a common metabolic engineering strategy to improve ATP pool in E. coli. By combinatorial genes manipulation, the L-arginine titer and yield increased by 17.9% and 28.9% in a 5-L bioreactor without betaine addition. This study revealed the molecular mechanism of gene transcription regulation by betaine and developed a superior L-arginine overproducer that does not require betaine.

Bioplastic production in terms of life cycle assessment: A state-of-the-art review

The current transition to sustainability and the circular economy can be viewed as a socio-technical response to environmental impacts and the need to enhance the overall performance of the linear production and consumption paradigm. The concept of biowaste refineries as a feasible alternative to petroleum refineries has gained popularity. Biowaste has become an important raw material source for developing bioproducts and biofuels. Therefore, effective environmental biowaste management systems for the production of bioproducts and biofuels are crucial and can be employed as pillars of a circular economy. Bioplastics, typically plastics manufactured from bio-based polymers, stand to contribute to more sustainable commercial plastic life cycles as part of a circular economy in which virgin polymers are made from renewable or recycled raw materials. Various frameworks and strategies are utilized to model and illustrate additional patterns in fossil fuel and bioplastic feedstock prices for various governments' long-term policies. This review paper highlights the harmful impacts of fossil-based plastic on the environment and human health, as well as the mass need for eco-friendly alternatives such as biodegradable bioplastics. Utilizing new types of bioplastics derived from renewable resources (e.g., biowastes, agricultural wastes, or microalgae) and choosing the appropriate end-of-life option (e.g., anaerobic digestion) may be the right direction to ensure the sustainability of bioplastic production. Clear regulation and financial incentives are still required to scale from niche polymers to large-scale bioplastic market applications with a truly sustainable impact.

Poly(3-hydroxybuyrate) production from industrial hemp waste pretreated with a chemical-free hydrothermal process

In this study, a mild two-stage hydrothermal pretreatment was employed to optimally valorize industrial hemp (Cannabis sativa sp.) fibrous waste into sugars for Poly(3-hydroxybuyrate) (PHB) production using recombinant Escherichia coli LSBJ. Biomass was pretreated using hot water at 160, 180, and 200°C for 5 and 10 minutes (15% solids), followed by disk refining. The sugar yields during enzymatic hydrolysis were found to improve with increasing temperature and the yields for hot water-disk refining pretreatment (HWDM) were higher compared to only hot water pretreatment at all conditions. The maximum glucose (56 g/L) and cellulose conversion (92%) were achieved for HWDM at 200°C for 10 minutes. The hydrolysate obtained was fermented at a sugar concentration of 20 g/L. The PHB inclusion and concentration of 48% and 1.8 g/L, respectively, were similar to those from pure sugars. A pH-controlled fermentation resulted in a near bi-fold increase in PHB yield (3.46 g/L).

Process intensification of biopolymer polyhydroxybutyrate production by pseudomonas putida SS9: A statistical approach

There are numerous elements of daily life where plastic is employed, yet it is uncertain exactly when it will deteriorate. Poly-(3-hydroxybutyrate) (PHB), a biodegradable polymer, is viewed as a possible substitute for synthetic plastics made from petroleum. With Pseudomonas putida SS9, the current study sought to enhance operational conditions and nutritional factors to enhance PHB production. To maximize the impacts of operational factors, a combination of response surface modeling (RSM) and artificial neural networks (ANN) has been applied. PHB content was used as the response while the interaction effects of the factors were examined. The optimal parameters for PHB synthesis were further tested in a lab scale fermentor. Under optimal conditions, 13.83 g/L of C, 0.57 g/L of N, 0.59 g/L of P, the maximal productivity of PHB obtained with Pseudomonas putida SS9 is 12.89 g/L after 84 h. A mean square value of 15.7 with P < 0.0001 were obtained from the ANOVA results of quadratic polynomial model using RSM. The same construct was employed in MATLAB software to train a feed-forward ANN using the back-propagation approach, generating 12.88 g/L. The data indicated that a properly trained ANN model outperforms the RSM model in prediction. Furthermore, employing dairy waste (cheese whey) as a low-cost feedstock resulted in an equally proportionate PHB yield of 12.02 g/L. Therefore, cheese whey appeared to be a viable alternative carbon source over optimized synthetic media.

Bioconversion of waste-to-resources (BWR-2021): Valorization of industrial and agro-wastes to fuel, feed, fertilizer, and biobased products

The mitigation of greenhouse gas (GHG) emission is one of the major focuses of The Glasgow Climate Pact, a global agreement that is believed to accelerate climate action. Following the energy sector, industrial and agro-wastes are the major contributors to global GHG emission. With the rapid growth in population, affluence, and urbanization, the GHG emission from waste sector is likely to be further aggravated if timely measures are not taken to address this burning issue. Thus, a significant research and development efforts are being made in shifting conventional waste treatment approach to resource recovery from waste, incorporating a circular bioeconomy concept. There have been significant advances in technologies such as anaerobic digestion, composting, pyrolysis, algae farming, and microbial fuel cell for recovering resources from organic wastes. This virtual special issue (VSI), "Bioconversion of Waste-to-Resources (BWR-2021)", contains 25 manuscripts covering various aspects of wastes and residual biomass valorization to high value products, including development of new technologies, optimization of current technologies for more efficient utilization of wastes and residues. The key findings of each manuscript are briefly summarized here, which can serve as a valuable resource for researchers in the field of resource recovery from wastes.