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This study investigated the enhancement effect of N 2 - and Air-nanobubble water (NBW) supplementation on two-stage anaerobic digestion (AD) of food waste (FW) for separate production of hydrogen and methane. In the first stage for hydrogen production, the highest cumulative H 2 yield (27.31 ± 1.21 mL/g-VS added) was obtained from FW + Air-NBW, increasing by 38% compared to the control (FW + deionized water (DW)). In the second stage for methane production, the cumulative CH 4 yield followed a descending order of FW + Air-NBW (373.63 ± 3.58 mL/g-VS added) > FW + N 2 -NBW (347.63 ± 7.05 mL/g-VS added) > FW + DW (300.93 ± 3.24 mL/g-VS added , control), increasing by 24% in FW + Air-NBW and 16% in FW + N 2 -NBW compared to the control, respectively. Further investigations indicate that different gas–NBW may positively impact the different stages of AD process. Addition of N 2 -NBW only enhanced the hydrolysis/acidification of FW with no significant effect on methanogenesis. By comparison, addition of Air-NBW promoted both hydrolysis/acidification stage and methanogenesis stage, reflecting by the enhanced activities of four extracellular hydrolases at the end of hydrolysis/acidification and coenzyme F 420 at the end of methanogenesis, respectively. Results from this work suggest the potential application of Air-NBW in the two-stage AD for efficient renewable energy recovery from FW. Unlabelled Image • Air-NBW significantly enhanced H 2 and CH 4 yields from two-stage AD of FW. • Greater activities of hydrolases were detected under Air-NBW addition. • Air-NBW positively effected methanogenesis indicated by increased F 420 activity. [ABSTRACT FROM AUTHOR]

Environmental stress such as nutrient deprivation across multiple fields in nature causes physiological and biochemical changes in organism. Understanding the potential epigenetic modulations to phenotypic variation upon nutrient deprivation stress is crucial for environmental assessments. Here, the methyl-cytosine at single-base resolution was mapped across the whole genome and the methylation patterns and methylation levels coordinated with transcript analysis were systemically elaborated in zebrafish embryonic fibroblast cells under serum starvation stress. The down-regulated genes mainly annotated to the pathways of DNA replication and cell cycle that were consistent with cell physiological changes. Vast differentially methylated regions were identified in genomic chromosome and showed enrichment in the intron and intergenic regions. In an integrated transcriptome and DNA methylation analyses, 135 negatively correlated genes were determined, wherein the hub genes of gins2 , cdca5 , fbxo5 , slc29a2 , suv39h1b , and zgc:174160 were predominant responsive to the nutrient condition changes. Besides, nutrient recovery and DNA methyltransferases inhibitor supplements partly rescued cell proliferation with decrease of DNA methylation and reactivation of several depressed genes, implying the possible intrinsic relationships among cell physiological state, mRNA expression, and DNA methylation. Collectively, current study proved the broad role of DNA methylation in governing cellular responses to nutrient deprivation and revealed the epigenetic risk of starvation stress in zebrafish. Unlabelled Image • Starvation stress suppressed cell growth, viability, and proliferation in zebrafish cells. • Vast differentially methylated regions were identified in genomic chromosome with intron and intergenic regions. • The overrepresented pathways were involved in DNA replication, cell cycle, cell growth and death. • Nutrient recovery and DNMTs inhibitors supplement partly rescued cell proliferation with changed DNA methylation. [ABSTRACT FROM AUTHOR]

The starvation is a common and severe stress for animal survival and development. In aquatic environment, many fish suffer starvation stress in different extent because of the natural migration or feed limitation. When subjected to starved conditions, organisms will employ various adaptive physiological, biochemical, and behavioral changes to regulate metabolism and maintain homeostasis. In the present study, adult female zebrafish were deprived of feed for 1 to 3 weeks to detect the starved effects on adults and larvae. The results showed that biological indexes, RNA/DNA ratios, and nutritional indexes significantly decreased in the female fish after starvation. The number of mature follicles reduced while the average spawning diameter of oocytes increased. For the larvae, the maternal starvation stress distinctly delayed embryonic hatching, decreased larval body length, disrupted larval swimming ability, and reduced survival rate at early-life stages. Furthermore, we found that DNA methylation might conduce to the downregulated mRNA expression of anti-Müllerian hormone and cytochrome P450 aromatase in retarded ovaries under starved conditions. Significant effects on autophagic transcription were shown in maternal ovary and larvae responded to starvation stress. Taken together, our study systematically revealed the reproductive impairments of starvation stress and would facilitate the investigation of environmental stress in teleost fish. Unlabelled Image • Starvation affected biological indexes and nutritional indexes of female zebrafish. • Starvation reduced ovarian fecundity and disturbed oogenesis in zebrafish. • Maternal starvation impaired the development and fitness of larvae at early-life stages. • The mRNA expression of amh , cyp19a1a , and autophagic genes responded to starvation stress in zebrafish. [ABSTRACT FROM AUTHOR]