Exposure to different temperature regimes at early life stages affects hatching, developmental morphology, larval growth, and muscle cellularity in rainbow trout, Oncorhynchus mykiss.

In this study, the effects of temperature on hatching, yolk-sac absorption, larval metamorphosis, post-metamorphic growth, developmental morphology, and muscle cellularity were assessed in rainbow trout, during its early development (until 52 days post-hatching, dph). From the eyed-ova stage, embryos were exposed to either low (8 ± 1 °C, LT-8) or high (16 ± 1 °C, HT-16) temperatures until hatching. Following hatching, half of the sac-fry from LT-8 group were shifted to higher temperature (16 ± 1 °C, LHT-16), and half from HT-16 group were shifted to medium temperature (13 ± 1 °C, HMT-13), for larval rearing. Incubating the eyed-ova at 16 °C preceded the hatching by 6 days, synchronized hatching duration, and minimized hatchlings' size-variation. However, it yielded smaller and morphologically less developed individuals compared to those incubated continuously at 8 ± 1 °C. Post-hatch shifting of sac-fry to high and medium temperatures, respectively, from the initial low and high regimes differentially affected the length and weight of fish. The effect on length was immediate and temporary, but on weight, it appeared to be permanent. Red muscle hypertrophy was observed to be high in HT-16 and HMT-13 individuals (high-temperature incubated groups). White muscle hypertrophy was high in HT-16 and LHT-16 individuals (high post-hatch rearing temperature groups). The effect of early-life temperature regimes on developmental morphology was found to be strong at 22 dph (82.5%) and comparatively weak at 52 dph (65%). The post-hatch rearing temperature caused an immediate but temporary effect on fin development, mainly pectoral, caudal, and anal fin (seen only at 22 dph, not at 52 dph). Contrarily, incubation temperature affected fin position, in a delayed but persistent manner (subtle at 22 dph, but stronger at 52 dph). Overall, this study provides new insights on temperature-dependent changes in developmental morphology, muscle cellularity, and larval growth in rainbow trout and shows that incubation temperature affects ontogeny profoundly than post-hatch thermal regimes.

Emerging trends in high-solids enzymatic saccharification of lignocellulosic feedstocks for developing an efficient and industrially deployable sugar platform.

For the techno-commercial success of any lignocellulosic biorefinery, the cost-effective production of fermentable sugars for the manufacturing of bio-based products is indispensable. High-solids enzymatic saccharification (HSES) is a straightforward approach to develop an industrially deployable sugar platform. Economic incentives such as reduced capital and operational expenditure along with environmental benefits in the form of reduced effluent discharge makes this strategy more lucrative for exploitation. However, HSES suffers from the drawback of non-linear and disproportionate sugar yields with increased substrate loadings. To overcome this bottleneck, researchers tend to perform HSES at high enzyme loadings. Nonetheless, the production costs of cellulases are one of the key contributors that impair the entire process economics. This review highlights the relentless efforts made globally to attain a high-titer of sugars and their fermentation products by performing efficient HSES at low cellulase loadings. In this context, technical innovations such as advancements in new pretreatment strategies, next-generation cellulase cocktails, additives, accessory enzymes, novel reactor concepts and enzyme recycling studies are especially showcased. This review further covers new insights, learnings and prospects in the area of lignocellulosic bioprocessing.

Concurrent changes in thermal tolerance thresholds and cellular heat stress response reveals novel molecular signatures and markers of high temperature acclimation in rainbow trout.

The objective of this study was to better understand the molecular mechanisms which regulate acclimatory responses and thermal safety margins of rainbow trout (Oncorhynchus mykiss) at temperatures above physiological optimum. For this, we investigated the time course of changes in critical thermal tolerance thresholds and associated hepatic and renal transcript abundance of molecular markers related to cellular stress response, during high temperature acclimation. The experimental fish were initially acclimated to 17 °C and later exposed to a gradually raised elevated temperature regime (22 °C) for a period of 30 days. CTmax, CTmin and mRNA expression of candidate markers were examined before the thermal challenge (T0) and over the time-course (days) of high temperature exposure (T1, T3, T7, T15 and T30). With respect to organismal response, CTmax was significantly elevated at T3, but the degree of gain in heat tolerance was not persistent. Contrarily, we observed a gradual loss in cold tolerance with highest CTmin estimate at T30. Based on the time-course of mRNA expression, the studied markers could be categorized into those which were persistently elevated (hsp70a, hsp70b, hspa5, hsp90a, hsp90b, stip1 and serpinh1 in kidney and hsp90b in liver); those which concurred with changes in CTmin (hspbp1, hsp90b, stip1, gr1, hif1a, hyou1, tnfa and tlr5 in kidney); and those which concurred with changes in CTmax (hsp90a, serpinh1, tlr5 and lmo2 in liver). Apparently, transcriptional changes in kidney and liver reflected CTmin and CTmax trend, respectively. Expression profile of stip1 and tlr5 suggest that they are potential novel markers which could reflect thermal limits in rainbow trout. Hepatic metabolic markers were either initially elevated (alt, glud, g6pase1) or down-regulated at different time-points (ast2, gls1, fas, cpt1b, mtor), linked to gluconeogenesis and metabolic depression, respectively. Whereas, growth-axis markers showed no significant differences. Overall, this time-course analysis has revealed potential associations in organismal and tissue-specific cellular response to high temperature acclimation in a thermally sensitive coldwater ectotherm.

Augmented hydrolysis of acid pretreated sugarcane bagasse by PEG 6000 addition: a case study of Cellic CTec2 with recycling and reuse.

In an integrated lignocellulosic biorefinery, the cost associated with the "cellulases" and "longer duration of cellulose hydrolysis" represents the two most important bottlenecks. Thus, to overcome these barriers, the present study aimed towards augmented hydrolysis of acid pretreated sugarcane bagasse within a short span of 16 h using Cellic CTec2 by addition of PEG 6000. Addition of this surfactant not only enhanced glucose release by twofold within stipulated time, but aided in recovery of Cellic CTec2 which was further recycled and reused for second round of saccharification. During first round of hydrolysis, when Cellic CTec2 was loaded at 25 mg protein/g cellulose content, it resulted in 76.24 ± 2.18% saccharification with a protein recovery of 58.4 ± 1.09%. Filtration through 50KDa PES membrane retained ~ 89% protein in 4.5-fold concentrated form and leads to simultaneous fractionation of ~ 70% glucose in the permeate. Later, the saccharification potential of recycled Cellic CTec2 was assessed for the second round of saccharification using two different approaches. Unfortified enzyme effectively hydrolysed 67% cellulose, whereas 72% glucose release was observed with Cellic CTec2 fortified with 25% fresh protein top-up. Incorporating the use of the recycled enzyme in two-stage hydrolysis could effectively reduce the Cellic CTec2 loading from 25 to 16.8 mg protein/g cellulose. Furthermore, 80% ethanol conversion efficiencies were achieved when glucose-rich permeate obtained after the first and second rounds of saccharification were evaluated using Saccharomyces cerevisiae MTCC 180.

Temperature and oxygen related ecophysiological traits of snow trout (Schizothorax richardsonii) are sensitive to seasonal changes in a Himalayan stream environment.

In this study, we investigated the seasonal changes in key eco-physiological traits of a wild population of snow trout, Schizothorax richardsonii from river Gola in the Indian Himalayan region over one year. Live specimens (5.8-31.4 g) were electro-fished from their natural habitat during representative months of four seasons with notable differences in water temperature, oxygen concentration and saturation. After 24-72 h of captive-acclimation, the fishes were examined for upper and lower critical thermal limits (CTmax and CTmin), incipient lethal oxygen thresholds (ILOC and ILOS), apparent routine and maximum oxygen consumption rates (MO2rout and MO2max), and blood haemoglobin-haematocrit. Across the seasons, mean CTmin and CTmax values ranged from ∼0 to 34.6 °C, suggesting a relatively wide acute thermal tolerance range for this predominantly cold-water fish. Changes in the habitat's thermal condition during winter to summer was reflected in the CTmin (∼0-2.4 °C) and CTmax (31.7-34.4 °C) estimates, while the highest thermal scope (CTmax-CTmin; 33.2 °C) was recorded in autumn. Concurrently, the incipient lethal hypoxia threshold observed in autumn (ILOS-2.6% and ILOC-0.19 mgO2/L) was significantly lower than the other three seasons, possibly linked to warm-acclimation. The reduction in blood haemoglobin-haematocrit levels during winter could limit the oxygen carrying capacity, with possible reciprocations in thermal tolerance and aerobic metabolism. Concerning body mass corrected oxygen consumption, the apparent MO2rout was found to increase in a temperature-dependent manner from 150.3 mgO2/kg/h at 12 °C to 315.2 mgO2/kg/h at 26 °C, with Q10 ranging from 1.6 to 2.2. Whereas, changes in MO2max was not temperature sensitive (Q10 of 0.7-1.3), except during spring-summer (Q10-2), with lowest and highest measurements in spring and autumn (934 and 1514 mgO2/kg/h), respectively. Collectively, these data form the first information report on the seasonal plasticity in thermal and respiratory physiology of a Schizothoracine fish species, bearing significance for their conservation, aquaculture and habitat monitoring.