Intensification of Acidogenic Fermentation for the Production of Biohydrogen and Volatile Fatty Acids—A Perspective

Comprehensive review of microbial production of medium-chain fatty acids from waste activated sludge and enhancement strategy

Microbial production of versatile applicability medium-chain fatty acids (MCFAs) (C6-C10) from waste activated sludge (WAS) provides a pioneering approach for wastewater treatment plants (WWTPs) to achieve carbon recovery. Mounting studies emerged endeavored to promote the MCFAs production from WAS while struggling with limited MCFAs production and selectivity. Herein, this review covers comprehensive introduction of the transformation process from WAS to MCFAs and elaborates the mechanisms for unsatisfactory MCFAs production. The enhancement strategies for biotransformation of WAS to MCFAs was presented. Especially, the robust performance of iron-based materials is highlighted. Furthermore, knowledge gaps are identified to outline future research directions. Recycling MCFAs from WAS presents a promising option for future WAS treatment, with iron-based materials emerging as a key regulatory strategy in advancing the application of WAS-to-MCFAs biotechnology. This review will advance the understanding of MCFAs recovery from WAS and promote sustainable resource management in WWTPs.

An overview of fermentation in the food industry - looking back from a new perspective

Fermentation is thought to be born in the Fertile Crescent, and since then, almost every culture has integrated fermented foods into their dietary habits. Originally used to preserve foods, fermentation is now applied to improve their physicochemical, sensory, nutritional, and safety attributes. Fermented dairy, alcoholic beverages like wine and beer, fermented vegetables, fruits, and meats are all highly valuable due to their increased storage stability, reduced risk of food poisoning, and enhanced flavor. Over the years, scientific research has associated the consumption of fermented products with improved health status. The fermentation process helps to break down compounds into more easily digestible forms. It also helps to reduce the amount of toxins and pathogens in food. Additionally, fermented foods contain probiotics, which are beneficial bacteria that help the body to digest food and absorb nutrients. In today's world, non-communicable diseases such as cardiovascular disease, type 2 diabetes, cancer, and allergies have increased. In this regard, scientific investigations have demonstrated that shifting to a diet that contains fermented foods can reduce the risk of non-communicable diseases. Moreover, in the last decade, there has been a growing interest in fermentation technology to valorize food waste into valuable by-products. Fermentation of various food wastes has resulted in the successful production of valuable by-products, including enzymes, pigments, and biofuels.

Effects of citric acid and heterofermentative inoculants on anaerobic co-fermentation of Chinese cabbage waste and wheat bran

The effects of Lactobacillus buchneri, Lactobacillus hilgardii and citric acid on organic acid production, substrate consumption, protein degradation and microbial community were investigated in this study. The results indicated that combined inoculants induced a significant increase in levels of lactic acid (43 g/kg dry matter), acetic acid (14 g/kg dry matter), butyric acid (5 g/kg dry matter), total organic acid (60 g/kg dry matter) and ammonia nitrogen (20 g/kg total nitrogen). Furthermore, citric acid addition into the combined inoculants caused a significant increase in levels of acetic acid (12 g/kg dry matter), water-soluble carbohydrate (12 g/kg dry matter) and a reduction in ammonia nitrogen formation (22 g/kg total nitrogen). Microbiologically, combining inoculants and citric acid enriched Lactobacillus buchneri and Lactobacillus hilgardii and upregulated the functional pathways related to acid production and resistance. Collectively, combining citric acid and heterofermentative inoculants was beneficial to recycle Chinese cabbage waste in producing organic acids.

Potential and Restrictions of Food-Waste Valorization through Fermentation Processes

Food losses (FL) and waste (FW) occur throughout the food supply chain. These residues are disposed of on landfills producing environmental issues due to pollutants released into the air, water, and soil. Several research efforts have focused on upgrading FL and FW in a portfolio of added-value products and energy vectors. Among the most relevant research advances, biotechnological upgrading of these residues via fermentation has been demonstrated to be a potential valorization alternative. Despite the multiple investigations performed on the conversion of FL and FW, a lack of comprehensive and systematic literature reviews evaluating the potential of fermentative processes to upgrade different food residues has been identified. Therefore, this article reviews the use of FL and FW in fermentative processes considering the composition, operating conditions, platforms, fermentation product application, and restrictions. This review provides the framework of food residue fermentation based on reported applications, experimental, and theoretical data. Moreover, this review provides future research ideas based on the analyzed information. Thus, potential applications and restrictions of the FL and FW used for fermentative processes are highlighted. In the end, food residues fermentation must be considered a mandatory step toward waste minimization, a circular economy, and the development of more sustainable production and consumption patterns.

Succinic Production from Source-Separated Kitchen Biowaste in a Biorefinery Concept: Focusing on Alternative Carbon Dioxide Source for Fermentation Processes

This study presents sustainable succinic acid production from the organic fraction of household kitchen wastes, i.e., the organic fraction of household kitchen waste (OFHKW), pretreated with enzymatic hydrolysis (100% cocktail dosage: 62.5% Cellic® CTec2, 31%% β-Glucanase and 6.5% Cellic ® HTec2, cellulase activity of 12.5 FPU/g-glucan). For fermentation, A. succinogenes was used, which consumes CO2 during the process. OFHKW at biomass loading > 20% (dry matter) resulted in a final concentration of fermentable sugars 81–85 g/L and can be treated as a promising feedstock for succinic production. Obtained results state that simultaneous addition of gaseous CO2 and MgCO3 (>20 g/dm3) resulted in the highest sugar conversion (79–81%) and succinic yields (74–75%). Additionally, CH4 content in biogas, used as a CO2 source, increased by 21–22% and reached 91–92% vol. Liquid fraction of source-separated kitchen biowaste and the residue after succinic fermentation were successfully converted into biogas. Results obtained in this study clearly document the possibility of integrated valuable compounds (succinic acid) and energy (biogas) production from the organic fraction of household kitchen wastes (OFHKW).