Beta-glucans have been studied in animal species, from earthworms to humans. They are a heterogeneous group of glucose polymers found in fungi, plants, some bacteria, and sea weeds. The recognition of conserved microbial structures is a key aspect of metazoan immunity, and beta-glucans are emerging as major target for the recognition of fungal pathogens. However, the receptors and mechanisms by which this is achieved differ significantly between vertebrates and invertebrates. In this review, we will highlight the known receptors for beta-glucans and will discuss the various immune responses they can initiate, with some applications of these products, in both vertebrates and invertebrates.

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A six‐week feeding trial was conducted to determine the effect of butyric acid (BA) inclusion in diet on performance of Barramundi (Lates calcarifer). Fish (12.0 ± 0.2 g) were fed with four experimental diets contained 0.0 (control), 2.5, 5.0 and 10.0 g BA/kg in triplicate. Fish fed on 5 and 10 g BA/kg diets had higher growth and total alkaline protease and lipase activities than the other treatments. Fillet protein content in BA‐supplemented groups was higher than the control. Liver catalase activity was highest in 2.5 g BA/kg group compared with the other groups. The values of liver superoxide dismutase activity and serum total protein concentration in 5 and 10 g BA/kg treatments were higher than those in the control (p < .05). Moreover, the highest and the lowest levels of serum lysozyme activity were noticed in the 10 g BA/kg and the control groups, respectively (p < .05). Also, the highest respiratory burst activity was observed in fish fed 5 g BA/kg feed. Supplementing diet with 2.5 or 5 g BA/kg resulted in higher serum haemolytic activity in fish compared with the other groups. The number of red and white blood cells increased in fish fed BA‐supplemented diets compared with the control (p < .05). In conclusion, the results of this study showed inclusion of BA at 5 g/kg diet in L. calcarifer juveniles improved growth and upgraded the general health condition by enhancing fish antioxidant enzyme activities and haemato‐immunological responses.

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A s e le c tio n o f is o g e n i c y e a s t s t r a i n s ( w ith d e l e t i o n f o r g e n e s in v o lv e d in c e l l -w a l l s y n th e s is ) w a s u s e d t o e v a l u a te t h e i r n u tr i t i o n a l a n d i m m u n o s tim u la to r y c h a r a c t e r i s t i c s f o r g n o t o b io tic a lly -g r o w n A r te m ia . I n th e f ir s t s e t o f e x p e r i m e n t s th e n u tr i tio n a l v a lu e o f i s o g e n i c y e a s t s tr a in s ( e f f e c te d in m a n n o p r o t e i n s , g l u c a n , c h itin a n d c e l l-w a ll b o u n d p r o t e i n s y n th e s is ) f o r g n o to b io tic a lly -g r o w n A r t e m i a w a s s tu d ie d . Y e a s t c e l l-w a ll m u t a n t s w e r e a l w a y s b e t t e r f e e d f o r A r te m ia th a n t h e is o g e n i c w ild t y p e m a in ly b e c a u s e th e y s u p p o r t e d a h i g h e r s u r v iv a l b u t n o t a s t r o n g e r in d iv id u a l g r o w th . T h e d if f e r e n c e in A r te m ia p e r f o r m a n c e b e tw e e n W T a n d m u ta n ts f e e d i n g w a s r e d u c e d w h e n s ta t i o n a r y -p h a s e g r o w n c e l ls w e r e u s e d . T h e s e r e s u lts s u g g e s t t h a t a n y m u ta tio n a f f e c tin g th e y e a s t c e llw a ll m a k e -u p is s u f f ic ie n t to i m p r o v e th e d ig e s t i b i l i t y in A r te m ia . T h e s e c o n d s e t o f e x p e r i m e n t s , in v e s t ig a te s t h e u s e o f a s m a ll a m o u n t o f y e a s t c e l l s in g n o to b io tic A r te m ia to o v e r c o m e p a th o g e n ic it y o f V ib r io c a m p b e ll ii (V C ) . A m o n g a ll y e a s t c e ll s tra in s u s e d in th i s s tu d y , o n ly m n n 9 y e a s t ( le s s c e l l-w a ll b o u n d m a n n o p r o t e i n s a n d m o r e g lu c a n a n d c h itin ) s e e m s to c o m p le te l y p r o te c t A r te m ia a g a i n s t t h e p a th o g e n . I n c o m p l e t e p r o t e c t i o n a g a i n s t th e p a th o g e n w a s o b t a i n e d b y th e g a s l a n d c h s 3 m u ta n ts , w h ic h a r el a c k i n g th e g e n e f o r a p a r tic u la r c e l l -w a l l p r o te in a n d c h i t i n s y n th e s is , r e s p e c tiv e ly , r e s u l t i n g in m o r e g lu c a n . T h e r e s u l t w ith th e c h s 3 m u t a n t is o f p a r tic u la r i n te r e s t, a s its n u tr i tio n a l v a l u e f o r A r te m ia is c o m p a r a b l e to th e w ild ty p e . H e n c e , o n ly w'i.th th e c h s 3 s t r a i n , in c o n t r a s t to th e g a s l o r m n n 9 s tr a in s , t h e t e m p o r a r y p r o t e c t i o n to V C is n o t c o n c o m i t a n t w ith a b e t t e r g r o w th p e r f o r m a n c e u n d e r n o n -c h a lle n g e d c o n d itio n s , s u g g e s t i n g n o n -i n t e r f e r e n c e o f g e n e r a l n u tr i tio n a l e f f e c ts .

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Effect of nisin on biochemical and microbial quality and shelf life of vacuum packaged rainbow trout (Oncorhynchus mykiss) during 16 days storage at 4°C was investigated. According to the obtained results, nisin treated fish showed lower (p<0.05) and acceptable biochemical (Peroxide value, thiobarbituric acid-index, pH, and total volatile base nitrogen) and bacteriological (total viable counts, psychrotrophic viable counts, and lactic acid bacteria) attributes up to 16 days storage at 4°C compared with those treated without nisin. Furthermore, FAs composition analysis indicated that presence of the nisin preserved nutritional quality of fish lipid, so that nisin treated samples contained higher percentage (p>0.05) of essential FAs such as eicosapentaenoic acid and docosahexaenoic acid. This study concluded that treatment of the vacuum packaged rainbow trout with nisin resulted in improvement of quality and extension of shelf life of the fish from 12 to 16 days at 4°C.

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