Rhodotorula paludigena CM33 is an oleaginous yeast that has been demonstrated to accumulate substantial quantities of intracellular lipids and carotenoids. In this study, crude glycerol, a by-product of biodiesel production, was used as a carbon source to enhance the accumulation of lipids and carotenoids in the cells. The culture conditions were first optimized using response surface methodology, which revealed that the carotenoid concentration and lipid content improved when the concentration of crude glycerol was 40 g/L. Different fermentation conditions were also investigated: batch, repeated-batch, and fed-batch conditions in a 500 L fermenter. For fed-batch fermentation, the maximum concentrations of biomass, lipids, and carotenoids obtained were 46.32 g/L, 37.65%, and 713.80 mg/L, respectively. A chemical-free carotenoid extraction method was also optimized using high-pressure homogenization and a microfluidizer device. The carotenoids were found to be mostly beta-carotene, which was confirmed by HPLC (high pressure liquid chromatography), LC-MS (liquid chromatography-mass spectrometry), and NMR (nuclear magnetic resonance). The results of this study indicate that crude glycerol can be used as a substrate to produce carotenoids, resulting in enhanced value of this biodiesel by-product.

Serine/arginine splicing factors (SRSFs) are critical regulators of gene expression that influence alternative splicing through RNA binding via the RNA recognition motif (RRM). Circular RNAs (circRNAs) are a subset of non-coding RNAs that exhibit differential expression in WSSV-infected Litopenaeus vannamei. This study investigates the role of LvSRSF2 in regulating circRNA expression in response to WSSV infection. LvSRSF2 was highly expressed in hemocytes and upregulated during WSSV infection. Silencing LvSRSF2 using dsRNA significantly upregulated the expression of circRNAs (circ-Alpha2, circ-Anillin, circ-Hemocytin, circ-Nephrin, and circ-Toll) in both WSSV-infected and uninfected shrimps at 72 h post-injection with dsRNAs. Knockdown of LvSRSF2 also significantly reduced WSSV copy numbers at 24 h post-infection and extended shrimp survival, with knockdown shrimp surviving up to 9 d compared to the control group. In addition, circ-Hemocytin, an SRSF2-related circRNA, was predicted to interact with six miRNAs targeting immune-related genes such as Toll, STAT, NF-κB, and Vago4. Following WSSV infection, circ-Hemocytin expression increased at 24 and 48 hpi, and the immune genes STAT and Vago4 were also upregulated, suggesting a potential circRNA–miRNA–mRNA regulatory axis in shrimp antiviral defense. Furthermore, targeted suppression of circ-Hemocytin expression using siRNAs significantly reduced its expression without affecting the corresponding linear transcript and resulted in a notable decrease in WSSV load in shrimp gills, highlighting its potential role in antiviral defense.

This study evaluated the valorisation of two agro-industrial byproducts, defatted rice bran (DRB) and discarded surimi seafood crabsticks (DSSCs), as rearing substrates for the black soldier fly (BSF; Hermetia illucens L.) to enhance its nutritional value and ensure feed safety for food applications. Two feed types with five replicates were compared: a modified feed (MF, DRB:DSSCs = 9:1, w/w) and an organic waste mixture (OW). MF-fed insects exhibited faster larval development, higher protein content (8.81%) ( ) and improved essential-to-nonessential amino acid ratio (up to 93%), whereas OW-fed insects showed higher lipid accumulation. Arsenic derived from DRB remained within the European Union safety limits but warrants monitoring for potential bioaccumulation. Transcriptomic analysis revealed 711, 3757 and 5178 differentially expressed genes (DEGs) in larvae, prepupae and pupae, respectively. In MF-fed insects, genes associated with energy metabolism and growth regulation, such as ATP5A1, LYZ, LYZ2, HSPA5-BIP, GST, SOD1, TNNI3, TPM1, TRPL and EYS, were upregulated, whereas those associated with lipid metabolism and immune responses, such as LIPA, CAMK, SPZ and JUN, were downregulated. Kyoto Encyclopaedia of Genes and Genomes enrichment analysis indicated the activation of oxidative phosphorylation, protein digestion and absorption and insect hormone biosynthesis pathways. These molecular responses align with enhanced growth and nutrient assimilation in MF-fed BSFs. Therefore, the integration of rice bran and surimi seafood byproducts can support efficient, safe and sustainable BSF production for circular food systems.