Average Specific Growth Rate Research Articles

Growth and Biochemical Characteristics of Microalgae Chlorella vulgaris Grown on Various Combinations of Fish Waste Hydrolysate and Seaweed Hydrolysate

Background: to utilize the fish waste and seaweed as a media for the growth of microalgae Chlorella vulgaris and carbon sequestration. Methods: Culture of Chlorella vulgaris in the fish waste and seaweed hydrolysate, analysed the cell density, biomass, chlorophyll, carotenoid content, carbon-di-oxide sequestration and proximate of microalgae (Protein, Carbohydrate, Lipid and Ash). Result: In the combination of fish acid hydrolysate and sargassum sp., acidhydrolysate, the respective peak values of cell density, average specific growth rate, biomass, chlorophyll a and b, carotenoid contentand carbon-di-oxide sequestrated recorded are 4.26±0.06×106 cells/ml, 0.58 µ/day, 1.98±0.04 g/l, 5.59±0.09 µg/ml and 3.69±0.04 µg/ml, 3.64±0.05 µg/ml, 3.73±0.07 g/l/d in 3:6 combination. Corresponding protein, carbohydrate, lipid and ash content observed in the resultant algae are 51.77±0.6%, 15.4±0.2%, 10±0.53 and 7.08±0.4% respectively.

Enhanced competitiveness of Spirodela polyrhiza in co-culture with Salvinia natans under combined exposure to polystyrene nanoplastics and polychlorinated biphenyls

Micro- and nanoplastics (MNPs) and polychlorinated biphenyls (PCBs) are prevalent in the environment and pose potential threats to ecosystems. However, studies on the phytotoxicity of MNPs and PCBs on primary producers are limited. This study investigated the effects of polystyrene nanoplastics (PS-NPs, 10 mg/L) and 2,2′,5,5′-tetrachlorobiphenyl (PCB-52, 0.1 mg/L), on the growth of Spirodela polyrhiza and Salvinia natans, and their impact on plant competitive ability under co-culture conditions. Laser confocal microscopy images revealed that PS-NPs accumulated on the leaf and root surfaces of both species. Combined exposure to PS-NPs and PCB-52 significantly inhibited the average specific and relative growth rates (RGR) of both species, reduced chlorophyll a and b levels, and slightly increased carotenoid content, disrupting the photosynthetic system. PCB-52 exacerbated PS-NPs accumulation on plants, leading to increased hydrogen peroxide (H2O2) and superoxide anion (O2−) production in both roots and leaves. This affects the activity of superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MDA), and the soluble protein content. The combined treatment with PS-NPs and PCB-52 induced greater ecological stress in both species than the treatment with PS-NPs alone. In addition, the combined treatment with PS-NPs and PCB-52 significantly improved the relative yield and competition balance index of S. polyrhiza, indicating that PS-NPs + PCB-52 enhanced the competitive ability of S. polyrhiza when co-cultured with S. natans. This study confirmed the effects of co-exposure to PS-NPs and PCB-52 on aquatic plant growth and species competition, contributing to better insight into the ecological impacts of MNPs and organic pollutants.

A multitrophic culture system for the production of black soldier fly larvae (Hermetia illucens)

Goals number 2, 11 and 12 of the 17 sustainable development goals, enacted by the United Nations as part of the 2030 Agenda for sustainable development, aim to end hunger as a priority, create sustainable cities and above all encourage responsible consumption and production. With increasing world population and higher demand for food, we need to find ways of producing cheap sources of protein and lipid that may in turn be used as animal or aquaculture feed. A multitrophic system involving mealworm larvae (MWL, Tenebrio molitor) and black soldier fly larvae (BSFL, Hermetia illucens) was developed to transform fruit and vegetable kitchen waste into usable biomass. MWL, fed mainly on kitchen waste, reached an average prepupal length of 2.4 cm, fresh weight of 0.12 g and dry matter protein and lipid contents of 44.2% and 16.5% respectively, with an average specific growth rate (SGR) of 2.2%/day and a feed conversion ratio (FCR) of 7.9. Conversely, BSFL fed on a variety of feeds, including MWL frass, kitchen waste and oats, had an average prepupal length of 1.3 cm, fresh weight of 0.16 g and dry matter protein and lipid contents of 41.4% and 26.3% respectively, with an average SGR and FCR of 4.3%/day and 8.9 respectively. The BSFL fed MWL frass obtained some of highest SGR and lowest FCR values, with one group achieving 7.5%/day and 2.9 respectively. This investigation has demonstrated the feasibility of a multi-trophic production system using kitchen waste to feed MWL whose frass was in turn used to feed BSFL thereby producing protein- and lipid-rich biomass that can serve as animal or aquaculture feed.

Effects of four types of natural bait on water quality, feeding, growth, and antioxidant enzyme activity of Monopterus albus in a recirculating aquaculture system

Monopterus albus is one of China’s renowned and superior aquaculture species, with its seedlings mainly sourced from wild capture. One of the bottlenecks in M. albus aquaculture is the high mortality rate and low feeding initiation rate from stocking wild fry to the initiation of feeding. In production, trash fish is commonly used to wean M. albus juveniles onto feeding. In this study, we introduced three other natural feeds, earthworms (EW), yellow mealworms (YMW), and fly maggots (FM), with frozen trash fish (TF) serving as the control group, to evaluate the effects of these four natural feeds on the survival rate, feeding initiation, antioxidant enzymes activity, and body composition of M. albus juveniles under recirculating water aquaculture conditions. The experiment comprised four treatments, each with three replicates. Each replicate consisted of stocking 150 M. albus juveniles weighing 10.02 ± 0.89 g in size, raised for 5 weeks. The survival rate of the YMW group was 73.33%–85.33%, which was significantly higher than that of the other three bait groups (p < 0.05). The four bait groups showed no significant differences in final body weight and specific growth rate (SGR) (p > 0.05). The EW group showed the highest final body weight, with an average SGR of 2.73, whereas the YMW group had an average SGR of 1.87. The average daily feeding amount was significantly higher in EW and YMW groups than in the other two groups (p < 0.05). The percentage of feeding amount to fish weight in the EW group reached 7.3% in the fifth week. After 5 weeks of cultivation, NO2−-N content was significantly higher in the waters of the TF and EW groups than in the waters of the FM and YMW groups (p < 0.05), there was no significant difference in TAN content among the treatment groups (p > 0.05). Liver malondialdehyde content was significantly higher in the TF group than in the other bait groups (p < 0.05). GSH-Px activity was significantly higher in the EW group than in the FM group and YMW group. No significant differences in SOD and CAT activity and T-AOC were observed among the bait groups (p > 0.05). The increase in crude protein content was significantly higher in the TF group than in the FM group, but the increase in crude ash content was significantly lower in the TFgroup. In conclusion, Tenebrio molitor could potentially serve as one of the alternative feeds during the initial stages of M. albus juveniles stocking.

Growth and Survival of Hatchery-Reared White Teatfish Holothuria fuscogilva Cherbonnier, 1980 Juveniles in Different Feed Types Under Laboratory Conditions

The hatchery production and mariculture of the sea cucumber species Holothuria fuscogilva Cherbonnier, 1980, commonly known as white teatfish, represent a potential remedy for the decreasing population of this extensively exploited species, owing to its considerable nutritional and medicinal value. The Sea Cucumber Research and Development Center at Mindanao State University in Naawan is actively formulating a comprehensive protocol for the large-scale production of H. fuscogilva through hatchery methods. Within hatchery rearing for mass production, selecting an optimal feed type influences the growth and survival rates of H. fuscogilva juveniles. To address this, an experiment employing a complete block randomized design was executed, utilizing four distinct feed types—Navicula sp., tilapia waste + commercial probiotics (CP), Spirulina powder, and commercial feed (mixed feed for Penaeus monodon #1)—each replicated three times. This 90-day laboratory experiment involved 960 individuals of 90-day-old hatchery- reared H. fuscogilva juveniles with an initial weight of 0.11±0.004g. The results revealed that Navicula sp. and Spirulina powder significantly contributed to higher average body weight, average weight gain, growth rate, and specific growth rates compared to commercial feed and tilapia waste + CP. Notably, Navicula sp. demonstrated the highest % survival rate (87.92±3.88%) over the 90 days, surpassing the rates observed for tilapia waste + CP (63.75±7.11%), Spirulina powder (26.67±6.40%), and commercial feed (20.00±4.30%). These findings suggest that the Navicula sp. was the ideal feed for H. fuscogilva juveniles at this stage supporting better survival and growth.

Growth Performance and Nutrient Utilizations of Heterobranchus bidorsalis (Geoffory Saint Hilaire, 1809) Fed on Fermented Sorghum Bran Meal Diets

The growth of aquaculture faces a high cost of feed which is about 60% to 75% of total production costs. An effort should be made to increase the profit by reducing the cost of feed as minimal as possible. This study investigated the growth performance and nutrient utilizations of Heterobranchus bidorsalis fed on fermented sorghum bran meal diets. sorghum bran was fermented at 10% moisture for seven days and samples for proximate analysis were collected on the first, fourth and seventh day. The highest crude protein was obtained in seventh day fermentation with 17.59±1.53% and the lowest was obtained in the zero day (control) with 10.53±1.53. Four isoproteic diets (40% crude protein) were formulated at 25%, 50%, 75% and 100% inclusion level to replace maize meal. The diets were fed to H.bidorsalis for twelve weeks. The experimental fish were fed 5% body weight throughout the experiment. The results obtained from the feeding trial showed that the fish fed on 100% inclusion level shows significance difference (p<0.05) in mean weight gain compared to fish fed on other diets. The highest mean weight gain (MWG) was obtained in the fish fed on 100% inclusion level diet (D5) with 43.39±1.86g and the lowest was obtained in control diet (D1) with 28.97±0.54g. The highest Average Daily Growth (ADG) and Specific Growth Rate (SGR) were obtained in the fish fed on (D5) with 0.52±0.56 and 1.07±0.64 while the lowest were obtained in the fish fed on control diet with 0.35±0.51 and 0.91±0.65 respectively. The nutrient utilizations showed significant difference (p<0.05) in fish fed on (D5) compared to others. The highest feed conversion ratio (FCR) was obtained in fish fed on (D5) with 0.48±0.16 and the lowest was obtained in control with 0.41±0.24. The highest protein intake (PI), protein rating (PR) and protein growth rate (PGR) were obtained in the fish fed on (D5) with 43.12±1.27, 0.52±0.72 and 1.04±0.71 while the lowest were obtained in the fish fed on control with 29.99±0.71, 0.35±0.45 and 1.00±0.53 respectively. The highest Protein Efficiency Ratio (PER) was obtained in the fish fed on (D5) with 1.01±0.07 and the lowest was obtained in the fish fed 50% inclusion level diet (D3) with 0.95±0.62. The highest Apparent Net Protein Utilization (ANPU) and Apparent Net Lipid Utilization (ANLU) were recorded in the fish fed on (D5) with 23.35±0.92 and 161.22±0.26 while the lowest were recorded in the fish fed on (D1) with 14.68±1.05 and 131.27±0.74 respectively. This study revealed the positive effects of incorporating fermented Sorghum bran meal into the diet of H. bidorsalis.

Acute toxicity of nanoscale zeolitic imidazolate framework 8 (ZIF-8) to saltwater planktonic species Artemia salina and Nannochloropsis oculata.

Zeolitic imidazolate framework-8 nanoparticles (ZIF-8 NPs) are metal-organic frameworks (MOFs) that have gained significant attention in various fields due to their unique properties. They have potential applications in drug delivery, gas storage, and catalysis. However, their increasing use raises concerns about their potential environmental impact. Our study evaluates the effects of ≈90nm ZIF-8 NPs in two planktonic species, the green microalga Nannochloropsis oculata and the brine shrimp Artemia salina. After synthesis and characterization (SEM, EDS, BET, and DLS) of nanoporous ZIF-8 NPs, a growth inhibition test on microalgae (72h) and acute immobilization test on instar I and II of Artemia nauplii (48h) were conducted following, OECD 201 and ISO/TS 20787, respectively. The toxicity of ZIF-8 NPs to both species was time- and concentration-dependent. The 72-h median inhibitory concentration (IC50) of ZIF-8 NPs for N. oculata based on average specific growth rate and yield were calculated as 79.71 ± 8.55mg L-1 and 51.73 ± 5.16mg L-1, respectively. Also, the 48-h median effective concentration (EC50) of ZIF-8 NPs on immobilization rate of instar I and II were calculated as 175.09 ± 4.14mg L-1 and 4.69 ± 0.34mg L-1, respectively. Moreover, the swimming type of non-immobilized animals was affected by ZIF-8 NPs. These findings provide a good insight into the toxicity of nanoparticulate ZIF-8 to saltwater planktons and also confirm that instar II Artemia is more sensitive than instar I. This study demonstrated that ZIF-8 NPs, despite all their advantages, could have toxic effects on aquatic organisms. More studies are required to assess their potential environmental impact and develop strategies to mitigate their toxicity.

Species Selection for Profitable Commercial Fish Culture Through Biofloc Technology

Biofloc technology is a recent concept in Bangladesh, it has numerous advantages for enhancing aquaculture production in several countries, thereby contributing to achieve sustainable development goals. To identify the most suitable fish species for profitable commercial fish culture through Biofloc, a 100-day experiment was conducted at Pran Fisheries Project in Razapur Village, situated in Sreemangal Upazilla of Moulvibazar district, commencing in March 2021. The experiment comprised three treatments: Oreochromis niloticus, Anabus testudineus, and Labeo rohita with two replicates for each treatment. Water quality parameters were meticulously monitored to ensure optimal conditions. All treatments were conducted at a temperature of 26°C, with pH levels of 7.6-7.8, dissolved oxygen concentrations of 5-6 ppm. During the study, O. niloticus exhibited the highest body weight (66.23 ± 0.94) compared to A. testudineus (50.82 ± 0.94) and L. rohita (53.92 ± 0.17). Furthermore, L. rohita displayed a higher average daily weight gain (1.8 ± 0.003) and specific growth rate (3.29 ± 0.29). The best feed conversion ratio (FCR) was observed both for O. niloticus (0.98 ± 0.33) and A. testudineus (0.98 ± 0.03). In terms of survival rate, O. niloticus outperformed the other species, with a rate of 98%. However, O. niloticus demonstrated better aquaculture performance compared to the other species using biofloc technology. This research provides valuable insights in effective cultural techniques that can enhance fish production through biofloc technology, contributing to economic growth in aquaculture sector and national development. J. Bio-Sci. 31(1): 71-85, 2023

The Effect of Water Spinach on the Water Quality, Antioxidant System, Non-Specific Immune Response, Growth Performance, and Carbon Balance in Red Tilapia Production

In this study, the compound aquaculture model of red tilapia (O. mossambicus albina × O. urolepis hornorum) and water spinach (Ipomoea aquatica) was used to investigate the effect of water spinach rafts on the water quality, antioxidant system, non-specific immune response, and growth performance of red tilapia and the carbon balance of payments. Red tilapia is characterized by its high adaptability to different production environments and food sources, as one of the most productive fish in aquaculture, and is well accepted in the market due to its nutritional and organoleptic characteristics. The experiment lasted for nine weeks and included two systems: the red tilapia-water spinach raft aquaponics (AP) system with 10% cover ratio with water spinach floating beds, and the aquatic monoculture (AM) system with only red tilapia. The total phosphorus (TP), total nitrogen (TN), and nitrate nitrogen (NO−3-N) in the AM were higher than those in AP from the fifth to ninth week. On the second, third, fifth, and sixth weeks, the ammonia nitrogen (NH4+-N), in the AM was higher than those in the AP. From the seventh week, the pH of the AM was significantly lower than the AP, while the nitrite nitrogen (NO−2-N) was significantly higher than the AP. The water quality index of the AP was better than that of the AM, indicating that water spinach can remove the nutrients from aquaculture water bodies. The average daily gain and specific growth rate (SGR) of fish in AP were higher than those in the AM. The acid phosphatase (ACP), alkaline phosphatase (AKP), and catalase (CAT) activities in the hepatopancreas of red tilapia in the AP were also significantly higher than those in the AM, while the malondialdehyde (MDA) in the AP was lower than the AM. The serum ACP and CAT of red tilapia in the AP were also higher than those in the AM, while the MDA of fish in the AP was lower than the AM. The results showed that both the experimental group and the control group were carbon sources and released greenhouse gases into the atmosphere, but the total carbon emissions of the red tilapia and the water spinach symbiotic system in the experimental group was significantly lower than that of the control group (p < 0.05). These results demonstrated that the application of water spinach rafts in aquaponics can not only improve the water quality, but also improve the growth performance, antioxidant system and non-specific immune responses of red tilapia, while promoting the utilization of organic matter in the aquaculture system, improving the ecological benefits in terms of the carbon income and expenditure.

An Approach for the Estimation of Concentrations of Soluble Compounds in E. coli Bioprocesses.

Accurate estimations of the concentrations of soluble compounds are crucial for optimizing bioprocesses involving Escherichia coli (E. coli). This study proposes a hybrid model structure that leverages off-gas analysis data and physiological parameters, including the average biomass age and specific growth rate, to estimate soluble compounds such as acetate and glutamate in fed-batch cultivations We used a hybrid recurrent neural network to establish the relationships between these parameters. To enhance the precision of the estimates, the model incorporates ensemble averaging and information gain. Ensemble averaging combines varying model inputs, leading to more robust representations of the underlying dynamics in E. coli bioprocesses. Our hybrid model estimates acetates with 1% and 8% system precision using data from the first site and the second site at GSK plc, respectively. Using the data from the second site, the precision of the approach for other solutes was as fallows: isoleucine -8%, lactate and glutamate -9%, and a 13% error for glutamine., These results, demonstrate its practical potential.

A study of water depth on the growth and productivity of seaweed <i>Kappaphycus alvarezii</i>

This study aims to investigate the impact of varying the depth of water on the growth and productivity of seaweed Kappaphycus alvarezii. The study was carried out in the seas of Pallette. The research methodology used in this study incorporates three different planting depth treatments, specifically 1.5 meters, 3 meters, and 4 meters. In each treatment, 50 grams of Kappaphycus alvarezii seeds per bunch were used. The findings of this study indicate that seaweed cultivation at a depth of 1.5 m yields significantly favourable outcomes compared to the treatments conducted at depths of 3 m and 4 m, where growth is comparatively less optimal. This occurrence can be attributed to the diminished level of light penetration at such a depth. There is an inverse relationship between the depth of seaweed planting and the rate of weight gain. The optimal depth for seaweed cultivation for 42 days is 1.5 meters, with an average specific growth rate of 3% daily. On the contrary, the treatment carried out at a depth of 1.5 m showed the most substantial increase in biomass, averaging 122 g. Additionally, the maximum yield of seaweed was observed in the same treatment, precisely measuring 1,208 g/m2.

Effects of diets containing grape pomace on the growth, nutrition indices, and the quality traits of common carp (Cyprinus carpio).

The fish diet is one of the essential factors in the development of aquaculture. The purpose of present study was to evaluate using grape pomace as a main feed ingredient on growth performance, body chemical composition, survival rate, and morphological indices of the carp (Cyprinus carpio). 200 fish with an average weight of 7 ± 0.4 g were randomly distributed in four tanks for total of 56 days. The fish were fed with a diet containing 5%, 10%, and 15% grape pomace in different feeding groups designated as G1, G2, and G3. The average daily weight gain (g), weights gain (g), and specific growth rate (%) were significantly higher (p < .05) in G3 as compared to G1 and G2 groups. The lowest feed conversion ratio was recorded in G3 group. The morphological indices, condition factors, viscerosomatic index, and hepatosomatic index were significantly higher in G3 group as compared to other treatments. The protein, fat, moisture, and ash contents in the C. carpio fillets were significantly influenced by feeding rate. The results showed that grape pomace had a positive effect on growth, survival, and nutritional indices in the carp fish. According to the obtained results, grape pomace (150 g/kg food) can be considered as the diet component for the carp fish.

PERBEDAAN JUMLAH IKAT BIBIT TERHADAP PERTUMBUHAN RUMPUT LAUT (Kappaphycus alvarezii) MENGGUNAKAN METODE LONG LINE PANTAI AMAL KOTA TARAKAN

Seaweed is one of the fisheries commodities that is widely cultivated in Indonesia. The cultivation of seaweed (Kappaphycus alvarezii) in the Coastal Waters of Amal Baru, Tarakan City, is traditionally done using the longline method. The gillnet method is the most used method by seaweed farmers because it is flexible in choosing locations and relatively inexpensive. The research aims to determine the difference in the number of seaweed seedlings on the absolute and specific growth rates. This study used a Completely Randomized Design (CRD) with 4 treatments and 3 replications. Treatment P1 (1 bundle), P2 (2 bundles), P3 (3 bundles), and P4 (4 bundles). The results showed that the growth of seaweed seedlings with different numbers of bundles influenced absolute and specific growth rates. The best treatment was found in treatment P4 with an average absolute growth rate of 80.00% and an average specific growth rate of 100%.

EFFECT OF TOMATO PLANT DENSITY ON AQUAPONIC SYSTEM PRODUCTION

The need to increase food production and match the food security demands under climate change impacts generate the force for developing aquaponic system. An aquaponic system was established at the Central Laboratory for Agricultural Climate (CLAC), Egypt, to investigate the effect of tomato plant density (2, 4 and 6 plants / m2) on tomato and fish production as well as the quality of rare water. Nutrient film technique (3 m length) used to produce tomato integrated with aquaculture of tilapia fish. Vegetative growth characteristics and yield parameters of Tomato as well as tilapia yield parameters plus the nutrient contents of rare water were recorded. The revealed results indicated that increasing the tomato plant density from 2 up to 6 plants / m2 led to a decrease in the No. of leaves, total leaves area and plant height of tomato. The early and total yield of tomato per plant significantly increased by decreasing the plant density from 6 to 4 and 2 plants /m2. On the contrary, the highest total yield per m2 was given by tomato density 6 plants. Tilapia average weight of (g), tilapia total yield (Kg/m3), average daily gain (ADG) and specific growth rate % (SGR) results increased significantly by increasing the plant density of tomato from 2 and 4 up to 6 plants / m2. Increasing the tomato plant density led to decrease significantly NO3, P, K, Ca and Mg (ppm) values of fish rare water content during the season period due to increasing the removal of nutrients for tomato sake. The accumulation of nutrients in rare fish water increased by increasing the growth of fish tilapia. The highest results of NO3, P, K, Ca and Mg were recorded by tomato plant density 2 plants /m2 while 6 plants /m2 had the lowest nutrient contents. For sustainable food production, the study recommended the plant density of tomato 6 plants /m2. 18 tomato plants in 3 m NFT system length (6 plants/m2) integrated with 150 tilapia fish in 1 m3.

Natural zeolite pretreatment of anaerobic digestate as efficient and promising detoxification strategy to improve microalgae biomass production

This work describes a new detoxification approach for the valorization of anaerobic digestate through microalgal cultivation. In this context, adsorption columns packed with different doses of natural zeolite (clinoptilolite) were used to pretreat liquid digestate and remove recalcitrant compounds such as ammonium nitrogen. After 24 h of treatment with 100 g/L of zeolite, the initial ammonium concentration was successfully reduced from 163.2 to 37.5 mg NH4-N/L, achieving 77.0 % of NH4-N removal efficiency and 1.3 mg NH4-N/g of adsorption capacity. As opposed to the untreated digestate, the zeolite pretreatment showed a significant positive effect on Tetradesmus obliquus microalgae consortium growth, with an average specific growth rate of 0.16 d−1 combined with the removal of 99.1 and 73.3 % of NH4-N and PO4-P, respectively. The experimental findings of this study have the potential to unlock the development of microalgae-based processes for the bioremediation of liquid digestate with the concomitant production of valuable algal biomass.

Bio-decarbonization by microalgae: a comprehensive analysis of CO2 transport in photo-bioreactor

Microalgae biofilm is a typical porous structure where CO2 is converted by microalgae into organic matter. Therefore, CO2 transport and its distribution in porous biofilm are crucial for microalgae decarbonization and its energy utilization. In order to get detailed process information of CO2 transport and its bioconversion, a mathematical model considering the microalgae growth and its material consumptions was established for substances' flow and transport processes in an immersed microalgae biofilm reactor. Modeling results showed that CO2 concentration on the surface of biofilm reduced about 26.57% along the flow direction. Increased inlet CO2 concentration (0.2–5.2 ​mM) significantly promoted the average specific growth rate of biofilm, which was more dramatical at a low flow rate with an enhancement about 7.38 times. Essential reason for it is a synchronous increase on total transfer flux of CO2 (8.25 times by ϕ_CO2) and average CO2 consumption rate (7.48 times by ACR_CO2) in biofilm. However, such promotion gradually waned with a growing initial carbon supply concentration. Enhanced CO2 transport in biofilm caused by increasing culture medium's flow rate (1–6 ​mL ​min−1) doesn't always result in synchronous improvements on biofilm growth. At sufficient carbon supply, increased flow rate doesn't further effectively improve biofilm growth but greatly reduced CO2 removal. Whether increasing carbon supply concentration or flow rate, biofilm growth can't be significantly promoted unless the ϕ_CO2 and ACR_CO2 in biofilm were increased by almost the same level. This work provides a new and deeper mechanistic insight into macroscopic growth characteristics of biofilms from the perspective of CO2 transport in it, as well as providing some theoretical guidance towards the cultivation of immersed microalgae biofilm for bio-decarbonization.

Enhanced production rate of probiotic Enterococcus faecium A028 by repeated batch solid-state fermentation and its survival under hot air drying with cell-protective agents

Probiotic viability is an important aspect of animal feed additives. Enterococcus faecium A028, a potential probiotic, was isolated from the intestinal digestion track of chicken. Production rate of E. faecium A028 probiotic inoculum with high total viable cell count (TVC) was enhanced using repeated batch solid-state fermentation (RB-SSF). The probiotic strain grew well in soybean meal (SBM) with average TVC of over 9 LogCFU/g in all RB-SSF experiments. Average specific growth rate of E. faecium A028 in fermented SBM (FSBM) was 50% repeated batch ratio (RB ratio) for 0.37 h−1, and higher than the batch process (0.33 h−1). Probiotic inoculum production rate was enhanced by increasing the RB ratio. Highest total TVC production rate was 128.15 LogCFU/h at 90% RB ratio, while average TVC was 9.09 LogCFU/g. Total production of FSBM at 90% RB ratio was 1.6 times higher than batch fermentation. Different protective agents were investigated to increase the survival of E. faecium A028 during hot air drying. Maltodextrin (MTD) provided the highest survival rate at 83.9% during 24 h of drying. RB-SSF effectively enhanced the production rate of probiotic strain cultivation in SBM, while MTD acted as a cell-protective agent and maintained the survival of E. faecium A028 during thermal drying.

Microalgal cultures for the remediation of wastewaters with different nitrogen to phosphorus ratios: Process modelling using artificial neural networks

Microalgae have remarkable potential for wastewater bioremediation since they can efficiently uptake nitrogen and phosphorus in a sustainable and environmentally friendly treatment system. However, wastewater composition greatly depends on its source and has a significant seasonal variability. This study aimed to evaluate the impact of different N:P molar ratios on the growth of Chlorella vulgaris and nutrient removal from synthetic wastewater. Furthermore, artificial neural network (ANN) threshold models, optimised by genetic algorithms (GAs), were used to model biomass productivity (BP) and nitrogen/phosphorus removal rates (RRN/RRP). The impact of various inputs culture variables on these parameters was evaluated. Microalgal growth was not nutrient limited since the average biomass productivities and specific growth rates were similar between the experiments. Nutrient removal efficiencies/rates reached 92.0 ± 0.6%/6.15 ± 0.01 mgN L−1 d−1 for nitrogen and 98.2 ± 0.2%/0.92 ± 0.03 mgP L−1 d−1 for phosphorus. Low nitrogen concentration limited phosphorus uptake for low N:P ratios (e.g., 2 and 3, yielding 36 ± 2 mgDW mgP−1 and 39 ± 3 mgDW mgP−1, respectively), while low phosphorus concentration limited nitrogen uptake with high ratios (e.g., 66 and 67, yielding 9.0 ± 0.4 mgDW mgN−1 and 8.8 ± 0.3 mgDW mgN−1, respectively). ANN models showed a high fitting performance, with coefficients of determination of 0.951, 0.800, and 0.793 for BP, RRN, and RRP, respectively. In summary, this study demonstrated that microalgae could successfully grow and adapt to N:P molar ratios between 2 and 67, but the nutrient uptake was impacted by these variations, especially for the lowest and highest N:P molar ratios. Furthermore, GA-ANN models demonstrated to be relevant tools for microalgal growth modelling and control. Their high fitting performance in characterising this biological system can contribute to reducing the experimental effort for culture monitoring (human resources and consumables), thus decreasing the costs of microalgae production.

Hexavalent chromate bioreduction by a magnetotactic bacterium Magnetospirillum gryphiswaldense MSR-1 and the effect of magnetosome synthesis.

Magnetotactic bacteria (MTB) are receiving attention for heavy metal biotreatment due to their potential for biosorption with heavy metals and the capability of the magnetic recovery. In this study, we investigated the characteristics of Cr(VI) bioreduction and biosorption by an MTB isolate, Magnetospirillum gryphiswaldense MSR-1, which has a higher growth rate and wider reflexivity in culture conditions. Our results demonstrated that the MSR-1 strain could remove Cr(VI) up to the concentration of 40 mg L−1 and with an optimal activity at neutral pH conditions. The magnetosome synthesis existed regulatory mechanisms between Cr(VI) reduction and cell division. The addition of 10 mg L−1 Cr(VI) significantly inhibited cell growth, but the magnetosome-deficient strain, B17316, showed an average specific growth rate of 0.062 h−1 at the same dosage. Cr(VI) reduction examined by the heat-inactivated and resting cells demonstrated that the main mechanism for MSR-1 strain to reduce Cr(VI) was chromate reductase and adsorption, and magnetosome synthesis would enhance the chromate reductase activity. Finally, our results elucidated that the chromate reductase distributes diversely in multiple subcellular components of the MSR-1 cells, including extracellular, membrane-associated, and intracellular cytoplasmic activity; and expression of the membrane-associated chromate reductase was increased after the cells were pre-exposed by Cr(VI).

Effect of Pulsed Feeding of GIFT Strain of Tilapia in Biofloc System Using Inland Saline Water

Feed is one of the major inputs in aquaculture system and constitutes 60%–80% of total production costs of tilapia. Inappropriate selection of feed quality and the feeding strategy affects the feed utilization resulting in high food conversion ratio (FCR). A 60 days experiment was conducted to evaluate the growth performance and immuno-physiological responses of GIFT tilapia, (Oreochromis niloticus) by pulsed feeding under biofloc culture system in inland saline water. For the experiment, feeding pattern in pulsed was followed viz., in situ biofloc with daily feeding (T1), in situ biofloc with alternate day feeding (T2), in situ biofloc with every third day feeding (T3), in situ biofloc with no feeding (T4), and clear water control with daily feeding (C) each in triplicates. Biofloc based treatment receiving daily feeding (T1) resulted in significantly (P&lt;0.05) higher average body weight, weight gain, and specific growth rate (SGR) compared to control. T1 and C showed a significantly similar feed conversion ratio (FCR) and protein efficiency ratio (PER). Fish maintained in T4 grew the least and survival was lowest (85%). The immunological parameters showed a significant difference (P&lt;0.05) for nitroblue tetrazolium (NBT) and myeloperoxidase content whereas no significant difference (P&gt;0.05) for lysozyme activity was observed. Higher NBT activity was observed in biofloc based treatments compared to control. Activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activity were considerably higher (P&lt;0.05) in biofloc based treatments than control. Among biofloc based treatments the antioxidant activities were lower in T1. The carbohydrate metabolism enzymes lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) were lower in T1, T2, and T3 compared to control and T4. In conclusion, in-situ biofloc with daily feeding is found to be effective in growth improvement and to elicit immune-physiological responses in GIFT tilapia under pulsed feeding using biofloc based system.