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Background Amylases produced by fungi during solid-state fermentation are the most widely used commercial enzymes to meet the ever-increasing demands of the global enzyme market. The use of low-cost substrates to curtail the production cost and reuse solid wastes are seen as viable options for the commercial production of many enzymes. Applications of α-amylases in food, feed, and industrial sectors have increased over the years. Additionally, the demand for processed and ready-to-eat food has increased because of the rapid growth of food-processing industries in developing economies. These factors significantly contribute to the global enzyme market. It is estimated that by the end of 2024, the global α-amylase market would reach USD 320.1 million (Grand View Research Inc., 2016). We produced α-amylase using Aspergillus oryzae and low-cost substrates obtained from edible oil cake, such as groundnut oil cake (GOC), coconut oil cake (COC), sesame oil cake (SOC) by solid-state fermentation. We cultivated the fungus using these nutrient-rich substrates to produce the enzyme. The enzyme was extracted, partially purified, and tested for pH and temperature stability. The effect of pH, incubation period and temperature on α-amylase production using A. oryzae was optimized. Box–Behnken design (BBD) of response surface methodology (RSM) was used to optimize and determine the effects of all process parameters on α-amylase production. The overall cost economics of α-amylase production using a pilot-scale fermenter was also studied. Results The substrate optimization for α-amylase production by the Box – Behnken design of RSM showed GOC as the most suitable substrate for A. oryzae , as evident from its maximum α-amylase production of 9868.12 U/gds. Further optimization of process parameters showed that the initial moisture content of 64%, pH of 4.5, incubation period of 108 h, and temperature of 32.5 °C are optimum conditions for α-amylase production. The production increased by 11.4% (10,994.74 U/gds) by up-scaling and using optimized conditions in a pilot-scale fermenter. The partially purified α-amylase exhibited maximum stability at a pH of 6.0 and a temperature of 55 °C. The overall cost economic studies showed that the partially purified α-amylase could be produced at the rate of Rs. 622/L. Conclusions The process parameters for enhanced α-amylase secretion were analyzed using 3D contour plots by RSM, which showed that contour lines were more oriented toward incubation temperature and pH, having a significant effect ( p <  0.05) on the α-amylase activity. The optimized parameters were subsequently employed in a 600 L-pilot-scale fermenter for the α-amylase production. The substrates were rich in nutrients, and supplementation of nutrients was not required. Thus, we have suggested an economically viable process of α-amylase production using a pilot-scale fermenter.

Understanding the impact of various climate features on wave climate is important for effective coastal climate adaptation and mitigation strategy planning. In the present study, the effect of tropical and extra-tropical climate modes such as Indian Ocean Dipole (IOD), El Niño Southern Oscillation (ENSO) and Southern Annular Mode (SAM) on wind-wave climate of the Indian Ocean (IO) is studied using multiple linear regression of individual climate indices on relevant wind-wave parameters. There are two regions of importance for swell generation in the Indian Ocean - a region between 40° and 60° S in the Southern Ocean (SO) and another region in the Eastern Tropical Indian Ocean (ETIO; 10°–30° S, 60°–100 °E). SAM, the strongest inter-annual mode of the SO, generates swells in the 40°–60°S band throughout the year that eventually propagates to the entire North IO. Both the positive and negative phases of SAM generate swells from SO, but it’s genesis region vary meridionally depending on the phase of SAM. The positive phase of ENSO (LaNiña) generally reduce the westerly wind anomalies in the SO caused by a positive phase of SAM and hence reduce the swell generation from SO, but causes stronger south-easterlies in the ETIO, generating more swells from there. IOD that peaks in September–October–November period has its effect on swell generation limited to eastern equatorial IO. Our analysis suggests that interannual climate features are important in modulating wind-wave climate of IO and a basin-wide model set-up with an accurate representation of various interannual climate features is a prerequisite for accurate wave forecast.

The coastal flood during the tropical cyclone Tauktae, 2021, at Chellanam coast, Kerala, India, has invited wide attention as the wave overtopping severely affected coastal properties and livelihood. We used a combination of WAVEWATCHIII and XBeach to study the coastal inundation during high waves. The effect of low-frequency waves and the rise in the coastal water level due to wave setup caused the inundation at Chellanam, even during low tide with negligible surge height. Wave setup raised the water level at the coast with steep slopes to more than 0.6 m and peaked during low tide, facilitating wave breaking at the nearshore region. The coastal regions adjacent to these steep slopes were subjected to severe inundation. The combined effect of long and short waves over wave setup formed extreme wave runups that flooded inland areas. At gently sloping beaches, the longwave component dominated and overtopped the seawalls and damaged households along the shoreline. The study emphasizes the importance of longwave and wave setup and its interaction with nearshore bathymetry during the high wave. The present study shall lead to the development of a coastal inundation prediction system for the low-lying hot spots using the combination of WAVEWATCHIII and XBeach models.

In this research study effect of silane-treated pectin biopolymer from waste dragon fruit peel as filler in the vinyl based composite and its resistance against to load bearing properties when the composite under aging condition. Pectin biopolymer is extracted from dragon fruit peel and pineapple leaf fibre is reinforced into the composite. Both fibre and filler undergo silane treatment to enhance bonding strength. The composite is developed through a hand layup process, and compositional values are documented. The compositesare undergoes temperature aging at 60 °C for 30, 60, and 90 days in a hot air oven. According to results notably, specimen D2 shows minimal reduction in mechanical strength even after 90 days of temperature aging. The tensile strength remained at 118 MPa, flexural strength at 158 MPa, ILSS at 24 MPa, V-notch shear strength at 21.2 MPa, Izod impact at 4.77 J, and hardness at 77 Shore-D. This resilience suggests that the silane treatment on both fibre and pectin played a pivotal role in preserving the mechanical integrity of the composite material, even under prolonged thermal weakening. Similar improvements were observed in fatigue life counts too. The silane treated pectin adhere the fibre and resin well and maintain high structural rigidity. SEM analysis also revealed adhesion improved fibre, improved toughness with fibre, fibre breakage, and minimalfibrepull-out. Overall, these findings offer insights into enhancing composite material properties through the strategic use of silane-treated pectin biopolymer and pineapple fibre reinforcement when aiming for varying in temperature applicable zones such as automotives, structural and drones.

In this study aluminium 2024 metal matrix composite was fabricated with lithium, silicon nitride and composite containing both lithium and silicon nitride using stir casting route. XRD results presented for confirming the existence of the reinforcements after the fabrication of composite. These fabricated composite samples were subjected to DUCOM pin on disc wear testing machine to study its dry sliding wear behaviors. Load, Speed and time were varied for a constant sliding distance. The scanning electron microscope was used to analyze the worn surface of wear tested composite samples. This study reveals that the increased sliding speed and load decreases the wear rate. Addition of hard ceramic reinforcement such as silicon nitrides to the composite reduces the wear coefficient and hence wear resistance is increased as compared to unreinforced alloy. The reduction in wear coefficient is due to the formation of mechanically mixed layer which is induced by the addition of hard silicon nitride to the aluminium alloy.

Occurrence of phytoplankton bloom in the northern Arabian Sea (NAS) during the winter monsoon is perplexing. The convective mixing leads to a deeper and well-oxygenated (> 95% saturation) mixed layer. We encountered low chlorophyll conditions though the nutrient conditions were favorable for a bloom. The mean ratio of silicate (Si) to DIN (Dissolved Inorganic Nitrogen: nitrate + nitrite + ammonium) in the euphotic zone was 0.52 indicating a “silicate-stressed” condition for the proliferation of diatoms. Also, the euphotic depth was much shallower (~ 49 m) than the mixed layer (~ 110 m) suggesting the Sverdrup critical depth limitation in the NAS. We show that the bloom in this region initiates only when the mixed layer shoals towards the euphotic zone. Our observations further suggest that two primary factors, the stoichiometric ratio of nutrients, especially the Si/DIN ratio, in the mixed layer and re-stratification of the upper water column, govern the phytoplankton blooming in NAS during the later winter monsoon. The important finding of the present study is that the Sverdrup’s critical depth limitation gives rise to the observed low chl- a concentration in the NAS, despite having enough nutrients.

A faecal indicator bacteria, Escherichia coli (E. coli), is widely used in monitoring health of estuaries, where tidal amplitude plays a critical role in its variability. Mahanadi estuary, formed at the mouth of a major tropical river Mahanadi, has large socio-economic importance. This anthropogenically stressed estuary remains understudied with respect to E. coli. Hence, this study addressed E. coli variability in Mahanadi estuary with novel sampling strategy that can be implemented at other tropical estuaries. The sampling strategy includes simultaneous measurements, at lesser-saline upper-estuary and higher-saline lower-estuary, over a tidal cycle. Although no significant variability of E. coli was observed between upper and lower-estuary, overall average count was higher during low tide and lower during high tide attributed to salinity fluctuations. Intermittent surpass of E. coli counts above recommended limits in Mahanadi estuary, indicated potential health risk, thus demands for frequent water quality monitoring and management strategies.

Flower-like bismuth sulfide (Bi 2 S 3 ) nanostructures were synthesized from two sulfur sources, namely thiourea and thioacetamide, by microwave irradiation technique. The synthesized materials were annealed at 300 °C for 3 h. The characteristic properties of the as-prepared and annealed samples S1, AS1 (thiourea source) and S2, AS2 (thioacetamide source) were studied by XRD, SEM with EDS, XPS, UV–Vis spectra and FTIR analysis. The XRD analysis revealed that the annealing process had increased the crystallite size of the Bi 2 S 3 samples. The SEM images showed that the flower-like nanostructure of both the samples (S1and S2) was changed to spherical shape (AS1) and irregular shape (AS2) respectively after annealing. The EDS and XPS results confirm the purity and the presence of the Bi and S. The UV–Vis absorption spectra revealed that the optical band gap values of Bi 2 S 3 were reduced due to the annealing process. The FTIR spectra showed the functional groups present in the as-prepared and annealed Bi 2 S 3 samples. The annealed Bi 2 S 3 nanoparticles (AS1) showed remarkable photocatalytic activity and achieved 98.6% RhB dye degradation in 180 min. The rhodamine B (RhB) photodegradation was determined to follow a pseudo-first-order kinetic model, with a rate constant of 0.02142 min −1 being the highest. After three cycles, the annealed Bi 2 S 3 nano photocatalyst showed excellent reusability and stability.

The variability in zooplankton density and species composition in response to tidal oscillations were investigated in the lesser saline upper reaches (E1) and higher saline lower reaches (E2) of the Mahanadi Estuary, located at the mouth of the third largest river in Indian Peninsula. This is the first of its kind high frequency observation over the tidal cycle ranging from highest high tide to lowest low tide in this estuary revealing dynamic variability of zooplankton assemblages. Zooplankton abundance was higher during high tide in comparison to low tide, irrespective of salinity regimes. On the diurnal scale, it was higher at night in comparison to the day at both E1 and E2. The higher abundance of zooplankton groups such as Copepoda, Cladocera, and planktonic larvae during the night at E1 as well as E2 indicating an upward migration. Many of the zooplankton taxa (e.g., Pseudodiaptomus serricaudatus , Pseudodiaptomus sp., Acartia danae , Acrocalanus longicornis , Oithona sp., Corycaeus andrewsi ) migrated towards E1 due to tidal effect during high tide and maintained their position even during low tide. In contrast, the prevalence of limnetic taxa (e.g., Brachionus rubens , Polyarthra vulgaris , Bosminopsis deitersi , Moina micrura , Heliodiaptomus sp.) at E2 during low tide indicated a predominant riverine source. The tidal variability of Brachyura (zoea and megalopa) revealed different emergence times that indicated dispersal of zoeas to the adjacent Bay of Bengal and the return of magalopa to the Mahanadi Estuary. Species diversity index was higher during high tide, and prominent at E2. At E1, marine, fresh, marine-brackish, and marine-brackish-fresh zooplankton species dominated during high tide, while brackish-fresh taxa dominated during low tide. Differently, E2 was enriched with marine, marine-brackish, and marine-brackish-fresh taxa during high tide, whereas fresh, brackish-fresh, and marine-fresh dominated during low tide. Salinity and suspended matter influenced the dominant zooplankton taxa at E2 and E1, respectively. Zooplankton assemblages exhibited a pattern of prominent diurnal-spatial variation in comparison to the tidal scale in the Mahanadi Estuary. Overall, this study documented a very high zooplankton diversity (92 taxa belonging to 13 groups) and significant variations in species abundance which highlighted the importance of carrying out sampling over the tidal cycle at contrasting salinity regimes.