This study investigated the feasibility of direct butanol production from starchy food waste (without saccharification and nutrient supplementation). First, Clostridium saccharoperbutylacetonicum N1-4 was selected as an efficient starch-utilizing clostridia, and amylose was used by the strain more readily than amylopectin for solvent production. Furthermore, direct fermentation avoided substrate inhibition due to saccharification and produced 12.1 g/L of butanol at a production rate of 0.705 g/L/h and a yield of 0.402 C-mol/C-mol with a solid–liquid ratio of 1:1 (w/v). At a solid–liquid ratio of 1:2 (w/v), the maximum butanol production rate in the direct mode was 2.05 times higher than that in the saccharified mode. Elemental analysis demonstrated that the food waste analyzed was rich in trace elements and, hence, exogenous nutrient supplementation was unnecessary. Collectively, direct butanol production from food waste could function as a low-cost, highly efficient, and simple fermentative process, which is a promising strategy for food waste disposal.

Massively input and accumulated ammonium is one of the main causes of eutrophication in aquatic ecosystems, which severely deteriorates water quality. Previous studies showed that one of the commonly used macrophytes, Myriophyllum aquaticum, was capable of not only withstanding ammonium of high concentration, but also efficiently assimilating extracellular ammonium to constitutive amino acids and proteins. However, the genetic mechanism regulating such efficient nitrogen metabolism in M. aquaticum is still poorly understood. Therefore, RNA-based analysis was performed in this study to understand the ammonium regulatory mechanism in M. aquaticum in response to various concentrations of ammonium. A total of 7721 genes were differentially expressed, of which those related to nitrogen-transport, assimilation, and remobilization were highly-regulated in response to various concentrations of ammonium. We have also identified transcription factors and protein kinases that were rapidly induced in response to ammonium, which suggests their involvement in ammonium-mediated signalling. Meanwhile, secondary metabolism including phenolics and anthocyanins biosynthesis was also activated in response to various concentrations of ammonium, especially at high ammonium concentrations. These results proposed a complex physiological and genetic regulation network related to nitrogen, carbohydrate, transcription factors, and secondary metabolism for nitrogen use efficiency in M. aquaticum.

The bibliometric method was used in this study to analyze current advances in the anaerobic digestion (AD) of cellulose waste. The result shows that the number of articles increased rapidly after 2010, suggesting a growing interest in this field. The USA and China were the top two countries with the highest number of published articles. AD of cellulose waste is being actively explored in many countries, and partnerships between countries are being actively formed. The top three subject categories were Environmental Sciences & Ecology, Engineering, Energy & Fuels. The most widely published and influential journals were Bioresource Technology, Water Science and Technology, and Waste Management. The co-occurrence and trend analysis of author keywords indicates that current research is primarily focused on pretreatment and co-digestion. Microbial community analysis plays a crucial role in elucidating the mechanisms, and life cycle analysis (LCA) could evaluate the impact on the environment at different stages. Microbial community analysis and LCA will be the hotspots in the future. To some extent, this study helps to understand the current global status and trends of the related research.