Low and unstable digestion performance is a challenging issue for anaerobic digestion, which prompts researchers to develop new strategies. In addition to traditional approaches such as co-digestion, pre-treatment, and recirculation, some emerging strategies, namely additive processes and microaeration, have also been recognized and developed in recent years. Many studies have evaluated the effect of these strategies on digestion performance. However, their comprehensive analysis is lacking, especially regarding the mechanisms of the different strategies. This review presents a comprehensive overview of research progress on these strategies based on the latest research, considering the five main strategies listed above. Through critical thinking, a summary of their mechanism, reactor performance, and availability of these strategies is presented. The results demonstrate that the contribution of microaeration is mainly to balance the composition and activity of hydrolysis, acidogenesis, and methanogenic archaea. Recirculation and co-digestion mainly balance mass and reaction environments. Pre-treatment, such as removing lignin, reducing cellulose crystallinity, and increasing the substrate-specific surface area, makes the characteristics of the substrate more conducive to the digestion of microorganisms. The mechanism of additive strategies varies greatly depending on the type of additive, such as enhancing interspecies electron transfer through conductive materials, resisting adverse digestion conditions through functional microbial additives, and accelerating nutrient absorption by regulating the bioavailability of trace elements. Although these strategies have different mechanisms for promoting digestion performance, their ultimate effect is to allow the parameters of the reactor to reach an ideal status and then achieve a balance among the substance, microorganisms, and water in an anaerobic reactor.

Maize (Zea mays L.) is one of the most important cereal crops worldwide, and increasing the grain yield and biomass has been among the most important goals of maize production. The plant architecture can determine the grain yield and biomass to some extent; however, the genetic basis of the link between the plant architecture and grain yield/biomass is unclear. In this study, an immortal F9 recombinant inbred line population, derived from the cross Mo17 x Huangzao4, was used to detect quantitative trait loci (QTLs) for 3 traits associated with plant architecture under two nitrogen regimes: plant height, ear height, and leaf number. As a result, 8 and 10 QTLs were identified under the high nitrogen regime and low nitrogen regime, respectively. These QTLs mapped to chromosomes 1 (six QTLs), 2 (one QTL), 3 (one QTL), 7 (two QTLs), and 9 (eight QTLs), and had different genetic distances to their closest markers, ranging from 0 to 22.0 cM, explaining 4.7 to 20.5% of the phenotypic variance. Because of an additive effect, 9 and 9 could make the phenotypic values of traits increase and decrease to some extent, respectively. These results are beneficial for understanding the genetic basis of agronomic traits associated with plant architecture and for performing marker-assisted selection in maize breeding programs.

Heat stress is one of the major abiotic stresses affecting the growth, sporulation, colonization and survival of Trichoderma viride. This study aimed to gain a better insight into the underlying mechanism governing the heat stress response of T. viride Tv-1511. We analysed the transcriptomic changes of Tv-1511 under normal and heat stress conditions using RNA sequencing. We observed that Tv-1511 regulates the biosynthesis of secondary metabolites through a complex network of signalling pathways. Additionally, it significantly activates the anti-oxidant defence system, heat shock proteins and stress-response-related transcription factors in response to heat stress. TvHSP70 was identified as a key gene, and transgenic Tv-1511 overexpressing TvHSP70 (TvHSP70-OE) was generated. We conducted an integrated morphological, physiological and molecular analyses of the TvHSP70-OE and wild-type strains. We observed that TvHSP70 over-expression significantly triggered the growth, anti-oxidant capacity, anti-fungal activity and growth-promoting ability of Tv-1511. Regarding anti-oxidant capacity, TvHSP70 primarily up-regulated genes involved in enzymatic and non-enzymatic anti-oxidant systems. In terms of anti-fungal activity, TvHSP70 primarily activated genes involved in the synthesis of enediyne, anti-fungal and aminoglycoside antibiotics. This study provides a comparative analysis of the functional significance and molecular mechanisms of HSP70 in Trichoderma. These findings provide a valuable foundation for further analyses.

This study examined the impact of sodium propionate concentration (0–40 g/L) on the methanogenic archaea in an inoculum which was cultured in basal nutrient medium, exploring its mechanisms and nonlinear stress intensity. The results indicated that at low concentrations, propionate-maintained homeostasis of the anaerobic digestion (AD) system and enriched Methanosaeta. However, when the concentration exceeded 16 g/L, the stability of the AD system was disrupted. The methanogenic pathway shifted towards a predominantly hydrogenotrophic pathway, resulting in a significant increase in methane yield. Below concentrations of 28 g/L, the AD system gradually enhanced its ability to utilize propionate in an orderly manner. At concentrations of 24–28 g/L, genera (e.g., Advenella and Methanosarcina) were enriched to adapt to the high-VFA environment. This was accompanied by a significant upregulation of genes related to the methylotrophic and hydrogenotrophic pathways, effectively mitigating propionate inhibition and enhancing methanogenesis. Conversely, excess concentrations (>30 g/L) suppressed methanogenesis-related genes and led to methane production arrest despite activating specialized propionate-metabolizing bacteria such as genus Pelotomaculum schinkii. As such, an increase in the stress intensity of propionate promotes a change in the metabolic pathways of methanogens and increases methane production; however, excessive sodium propionate was not conducive to maintaining the steady state of the system.

Introduction: Melatonin (N-acetyl-5-methoxytryptamine) is a molecule implicated in multiple biological functions, but exerts contrasting effects on plants owing to concentration differences. Hydroxyindole O-methyltransferase (HIOMT), which catalyzes the last step of melatonin synthesis, plays a crucial role in this context.Methods: Transgenic switchgrass overexpressing oHIOMT with different melatonin levels displayed distinct morphological changes in a concentration-dependent manner. In this study, we divided the transgenic switchgrass into two groups: melatonin-moderate transgenic (MMT) plants and melatonin-rich transgenic (MRT) plants. To determine the concentration-dependent effect of melatonin on switchgrass growth and stress resistance, we conducted comparative morphological, physiological, omics and molecular analyses between MMT, MRT and wild-type (WT) plants.Results: We found that oHIOMT overexpression, with moderate melatonin levels, was crucial in regulating switchgrass growth through changes in cell size rather than cell number. Moderate levels of melatonin were vital in regulating carbon fixation, stomatal development and chlorophyll metabolism. Regarding salt tolerance, melatonin with moderate levels activated numerous defense (e.g. morphological characteristics, anatomical structure, antioxidant enzymatic properties, non-enzymatic capacity and Na⁺/K⁺ homeostasis). Additionally, moderate levels of oHIOMT overexpression were sufficient to increase lignin content and alter monolignol compositions with an increase in the S/G lignin ratio.Discussion: Taken together, oHIOMT overexpression in switchgrass with different melatonin levels resulted in morphological, anatomical, physiological and molecular changes in a concentration-dependent manner, which characterized by stimulation at low doses and inhibition at high doses. Our study presents new ideas and clues for further research on the mechanisms of the concentration-dependent effect of melatonin.