Novel approaches to microalgal and cyanobacterial cultivation for bioenergy and biofuel production.

Fresh fish is extensively consumed and is one of the most-traded food commodities in the world. Conventional preservation technologies include vacuum and modified atmosphere packaging, but they are costly since requires capital investment. In the last decade, research has been directed towards the development of antimicrobial packaging systems, as an economical alternative to these. This paper outlines antimicrobial films and coatings applied so far on fresh fish, their efficacy against targeted microorganism/group and effects on chemical quality of the product. Findings show that edible films/coatings incorporated with different active agents applied to fresh fish are able to inhibit the microbial growth and decrease the rate of fish nutrients degradation, thus preventing the formation of chemical metabolites; a shelf-life extension of 6 to 13 days was obtained for fish fillets, depending on the species on which the active packaging materials were applied. The manufacturing use of these formulations could lead to a significant reduction in fish waste, consequently, a diminution of economic losses for fish traders and retailers. Therefore, their industrial production and commercialization could be an exploitable sector by the packaging industry.

https://www.mdpi.com/2079-6412/8/10/366/pdf

Edible Films and Coatings for Fresh Fish Packaging: Focus on Quality Changes and Shelf-life Extension

Financial Management in Agriculture

Contaminant loads derived from land-use intensification, such as nutrients, sediment and microorganisms, are a particular concern for vulnerable and sensitive waterbodies. While a number of diffuse nutrient pollution mitigation systems are currently available, these are not yet widely applied or where they have been, some residual contaminants are still lost from the land. Adoption of, efficient mitigation systems that can be applied to a range of land types and environments, operate along pollution gradients and are cost-effective at a range of scales are therefore vital to meet the strategic objectives of freshwater management, whilst supporting economic growth. Periphyton nutrient removal systems (PNRS) are a biological-based mitigation system that is capable of treating diffuse nutrient pollution in waterways, resulting in reduced nutrient loads to downstream waterways. During photosynthesis and growth, the algal component of the periphyton matrix quickly assimilates dissolved nitrogen and phosphorus from the overlying water into its biomass. Nutrient assimilation coupled with periodic harvesting of the algal biomass to permanently remove these nutrients from the waterway provides an opportunity to exploit periphyton for diffuse nutrient pollution mitigation. Current research indicates that such systems would have half the land requirements of a wetland treatment system for the same nitrogen removal rate as well as less capital costs and require only weeks to become fully established. PNRS have the added benefit of resource recovery for beneficial re-use for food, fertiliser, or biofuel. Further research is needed on the optimisation of PNRS design and operation to enhance performance. This research would help inform the adaption of PNRS to suit local climatic conditions, nutrient pollution type and level and treatment objectives.

Utilising periphytic algae as nutrient removal systems for the treatment of diffuse nutrient pollution in waterways

The potential of biofilm-based photobioreactors (PBRs) for various applications has long been recognized, and various types of biofilm-based PBRs have been developed for different applications. Compared to suspension-based PBR reactors, biofilm-based systems offer several advantages, including a significantly higher biomass concentration. However, due to the immobilization of the cells, in contrast to suspension-based systems, dissolved inorganic carbon (DIC) has to be transferred into the biofilm for consumption. Thus, to ensure efficient operation of these systems under a given lighting scheme (e.g. depending on geographical location), availability of DIC should be optimized. To achieve this, the dynamics of DIC inside the various biofilm-based PBRs, as well as the operational principles of these PBRs, need to be understood. The mini-review summarizes the designs of existing biofilm-based PBRs and reviews previous studies on DIC dynamics in various biofilms. Strategies to enhance DIC availability for the immobilized cells in biofilm-based PBRs are also discussed.

Biofilm-based photobioreactors: their design and improving productivity through efficient supply of dissolved inorganic carbon.

Ongoing research in recirculation aquaculture focuses on evaluating and improving the purification potential of different types of filters. Algal Turf Scrubber (ATS) are special as they combine sedimentation and biofiltration. An ATS was subjected to high nutrient loads of catfish effluent to examine the effect of total suspended solids (TSS), sludge accumulation and nutrient loading rate on total ammonia nitrogen (TAN), nitrite and nitrate removal. Nutrient removal rates were not affected at TSS concentration of up to 0.08 g L-1 (P > 0.05). TAN removal rate was higher (0.656 ± 0.088 g m-² day-1 TAN) in young biofilm than (0.302 ± 0.098 g m-² day-1 TAN) in mature biofilm at loading rates of 3.81 and 3.76 g m-² day-1 TAN (P 0.05). The ATS ably removed nitrogen at high rates from catfish effluent at high loading rates. ATS-based nitrogen removal exhibits high potential for use with high feed loads in intensive aquaculture.

Removal of nitrogen by Algal Turf Scrubber Technology in recirculating aquaculture system

Fish are a nutrient rich food but highly perishable due to its high water activity, protein content, neutral pH and presence of autolytic enzymes. This explains why fresh fish quality deteriorates rapidly if not properly stored after catch such as use of low temperature. The implication is that delayed processing of fresh fish negatively influences consumer taste of fish. Further, fresh fish that are not processed on time lose nutrients due to spoilage. In Malawi, most fresh fish are sold in the open due to lack of storage facilities such as refrigerators – a condition that accelerates spoilage of fish. This study was carried out to assess the effect of delayed processing on nutrient composition, pH level and organoleptic quality of pond raised tilapia - Oreochromis shiranus which is the commonest grown tilapia in Malawi. Thirty freshly pond harvested O. shiranus fish (average weight 100g) were cleaned then deep fried in edible cooking vegetable oil at time intervals of 0, 6 and 12 hours from catch and stored at ambient temperature. A pre-trained sensory evaluation panel consisting six members described changes in the sensory quality of the fresh and fried fish at every sampling time interval. Crude protein, crude fat, ash, moisture content and pH were also determined at each sampling time. Determined crude protein and crude fat decreased while ash content increased with storage time though these were not significantly different from baseline (P>0.05). Moisture content decreased from 0 (fresh) to 6 hours then increased again up to 12 hours of storage. Ash and moisture content correlated positively (0.93 and 0.79% respectively), whilst crude protein, crude fat and pH were negatively correlated (-0.91, -0.05 and -0.97, respectively) to sensory quality demerit scores. pH decreased from 5.94 at 0 hours to 5.92 after 6 hours then increased sharply to 5.98 after 12 hours of ambient fish storage. Consumers started to significantly (P<0.05) dislike the fish after 7 hours and eventually rejected the samples after 12 hours of ambient storage time. The study recommends that for optimum consumer satisfaction and nutritional benefit, fresh O. shiranus should be processed at most 7 hours after harvesting. Key words : Nutrients, taste, Tilapia, ambient storage

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Effect of delayed processing on nutrient composition, pH and organoleptic quality of pond raised tilapia (Oreochromis shiranus) stored at ambient temperature

A study was conducted to assess the effect of temperature on egg development in an attempt to improve hatching success and fry production in Oreochromis karongae. Temperature-dependent development rates and hatching period for fertilized eggs stripped from O. karongae, a mouth brooder, were determined in a recirculating system set up in a hatchery at the National Aquaculture Center, Domasi, Malawi. Three treatments namely; 25, 27 and 29EsC, were replicated thrice in 2-L Macdonald type incubation jars stocked with 265 fertilized stage 1 eggs of O. karongae, at water flow rate of 0.15 L/s. There was a curvilinear relationship between temperature and egg development, which was best described by a logarithm regression function. Hatching period decreased with increase in incubation temperature. The shortest hatching period was 7.3 days, which was observed at the highest incubation temperature (29°C) while the longest hatching period was 14.7 days, observed at the lowest temperature (25°C). Hatchability and fry survival were higher at higher temperatures. The study has, for the first time, ably described O. karongae egg development rates which suggest that increasing incubation temperature holds the potential to increase fry production, which is currently a bottleneck.

	 

	Key words: Oreochromis karongae, temperature-dependent, egg development rates, hatchability, survival, hatching period.

Temperature-dependent egg development rates, hatchability and fry survival rate of Lake Malawi Tilapia (Chambo), Oreochromis karongae (Pisces: Cichlidae)

An on-farm study was conducted in Chingale area in Zomba, Southern Malawi to assess the growth of three tilapia fish species in earthen ponds of different sizes and water depths. The experiment was laid out in a factorial design of 200 and 400 m2 pond sizes, 0.8 and 1.2 m pond water depths, and fish species: Oreochromis karongae, Oreochromis shiranus and Tilapia rendalli, replicated thrice among randomly selected farmers. Ponds were fertilized monthly with fresh chicken manure at an application rate of 1 ton/ha and fish were fed on maize bran as a supplement at 5% body weight. Fish were sampled and weighed every four weeks over 6 months. O. karongae attained the highest weight gain (65.75 g) in smaller ponds (200 m2) translating into an overall higher gross yield of 2.91 tons/ha/year (P 0.05). Fish in deeper ponds had a significantly higher overall mean final weight (52.26 g) (P<0.05). T. rendalli exhibited the lowest average daily weight gain (0.27) especially in 200 m2 ponds, but had the highest specific growth rate (1.65%) while overall, O. karongae was the most advanced of the three tilapia species in terms of growth. Findings from this study suggest that for small-commercial fish farmers, smaller but deeper ponds produce better fish production results, hence should be adopted.

	Key words: Tilapia, pond water depth, pond size, weight gain.

/pdf/growth-performance-of-three-tilapia-fish-species-raised-at-32cb0dx6b0.pdf

Growth performance of three tilapia fish species raised at varied pond sizes and water depths

Malawi’s demographic dividend remains low with a population that is young, comprising 46% below the age of 15. The majority of the population is involved in agriculture, which is the backbone of the economy; however, there has been limited investment, especially in agriculture higher education. There remains a big gap between higher education and development. A study was therefore undertaken to understand current status and identify challenges and opportunities in higher education, with special focus on agriculture. Literature was reviewed and the public, private sector and civil society were consulted using checklists. Findings show that Malawi has four public universities and sixteen private universities registered with the National Council for Higher Education. None of the universities is highly ranked in the global ranking systems for higher education instituons. This is as a result of limited research and publications, limited funding, poor infrastructure, non-industry oriented curriculum and compromised quality of education. Therefore, universities should intensify interaction with industry to improve research, curriculum design and delivery and graduate training and research quality. The National Council for Higher Education in Malawi and line ministry should develop a national qualifications framework, in reference to international standards, to guide and regulate quality of university programmes. Overall, the government and development partners should prioritize investing in the young generation to advance to higher education in order to reap a significant demographic dividend and foster development. Key words: Agriculture, demographic dividend, investment, University ranking

http://www.afjrd.org/jos/index.php/afjrd/article/download/70/32

Joshua Valeta

Papers

Removal of nitrogen by Algal Turf Scrubber Technology in recirculating aquaculture system

Effect of delayed processing on nutrient composition, pH and organoleptic quality of pond raised tilapia (Oreochromis shiranus) stored at ambient temperature

Temperature-dependent egg development rates, hatchability and fry survival rate of Lake Malawi Tilapia (Chambo), Oreochromis karongae (Pisces: Cichlidae)

Growth performance of three tilapia fish species raised at varied pond sizes and water depths

Status of Higher Education, Science and Technology in Malawi: A focus on Agricultural Higher Education