盐度对花鳗鲡和太平洋双色鳗鲡幼鳗生长性能及消化酶活力的影响

文章研究了不同盐度对花鳗鲡(Anguilla marmorata)幼鳗和太平洋双色鳗鲡(A. bicolor pacifica)幼鳗生长性能及消化酶活力的影响。将花鳗鲡幼鳗(9.760.36) g和太平洋双色鳗鲡幼鳗(11.820.04) g分别在淡水(盐度0)与盐度5、10、18水体中养殖30d, 测量每组实验鱼总重后检测胃、肠道和肝脏蛋白酶、淀粉酶和脂肪酶的活力。结果表明, 花鳗鲡和太平洋双色鳗鲡在各盐度处理中存活率均为100%, 未出现死亡。两种鳗鲡在淡水中生长良好, 特定生长率最高, 而饵料系数最低。盐度对花鳗鲡幼鳗和太平洋双色鳗鲡幼鳗消化酶活力的影响存在差异, 其中花鳗鲡胃、肠道和肝脏蛋白酶活力在各盐度处理中均无显著变化(P0.05), 淀粉酶和脂肪酶活力均随盐度的增加而下降; 太平洋双色鳗鲡胃蛋白酶活力在盐度10时最大, 肝蛋白酶活力在盐度18时最大, 而淀粉酶和脂肪酶活力在各盐度处理组无显著变化(P0.05)。这表明盐度对花鳗鲡胃、肠道和肝脏的淀粉酶和脂肪酶活力具有抑制作用, 对太平洋双色鳗鲡的蛋白酶活力有一定的激活作用。在相同盐度条件下, 不同消化器官中同种消化酶活力存在差异, 各盐度的两种鳗鲡肠道中淀粉酶和脂肪酶的活力均显著高于肝脏和胃(P0.05), 胃中蛋白酶活力高于肝脏和肠道, 但不显著(P0.05)。研究发现两种鳗鲡体内脂肪酶活力相对较高, 表明其对脂肪具有较强的消化能力。建议在配制花鳗鲡幼鳗和太平洋双色鳗鲡幼鳗饲料时, 适当提高粗脂肪比例, 有助于促进对营养物质的消化吸收, 提高养殖效益。       

Characterization of Bioactive Actinomycetes Isolated from Kadolkele Mangrove Sediments,Sri Lanka

Exploring untapped microbial potentials in previously uncharted environments has become crucial in discovering novel secondary metabolites and enzymes for biotechnological applications. Among prokaryotes, actinomycetes are well recognized for producing a vast range of secondary metabolites and extracellular enzymes. In the present study, we have used surface sediments from ‘Kadolkele’ mangrove ecosystem located in the Negombo lagoon area, Sri Lanka, to isolate actinomycetes with bioactive potentials. A total of six actinomycetes were isolated on modified-starch casein agar and characterized. The isolates were evaluated for their antibacterial activity against four selected bacterial strains and to produce extracellular enzymes: cellulase, amylase, protease, and lipase. Three out of the six isolates exhibited antibacterial activity against Staphylococcus aureus, Escherichia coli, and Bacillus cereus, but not against Listeria monocytogenes. Five strains could produce extracellular cellulase, while all six isolates exhibited amylase activity. Only three of the six isolates were positive for protease and lipase assays separately. Ac-1, Ac-2, and Ac-9, identified as Streptomyces spp. with the 16S rRNA gene sequencing, were used for pigment extraction using four different solvents. Acetone-extracted crude pigments of Ac-1and Ac-2 were further used in well-diffusion assays, and growth inhibition of test bacteria was observed only with the crude pigment extract of Ac-2. Further, six different commercially available fabrics were dyed with crude pigments of Ac-1. The dyed fabrics retained the yellow color after acid, alkaline, and cold-water treatments suggesting the potential of the Ac-1 pigment to be used in biotechnological applications.     

马蜂肠道菌的分离鉴定及产消化酶功能菌株的筛选

【背景】马蜂(Vespa mandarinia Smith)可以防治多种田间害虫,还具有药用价值,其肠道菌群结构和功能还有待研究。【目的】获得马蜂肠道可培养细菌并筛选出具有产消化酶功能的菌株,为理解肠道菌对宿主的影响机理及功能菌株的利用提供科学依据和研究材料。【方法】采用传统细菌分离培养法获得马蜂肠道菌,结合形态学以及16S rRNA基因序列分析进行鉴定;利用水解圈法分别筛选产蛋白酶、脂肪酶、淀粉酶和纤维素酶菌株;通过测量水解圈D与菌落直径d的比值,比较不同细菌的产酶能力。【结果】在马蜂肠道中共分离出6属10种细菌,其中芽孢杆菌属5种,肠球菌属、葡萄球菌属、明串珠菌属、乳球菌属和不动杆菌属各1种。从获得的61个菌株中筛选出6个具有产消化酶功能的菌株。其中,苏云金芽孢杆菌V44具有产蛋白酶、淀粉酶、脂肪酶和纤维素酶4种消化酶的能力;粪肠球菌V6具有产淀粉酶、蛋白酶和脂肪酶3种消化酶的能力;蜡样芽孢杆菌V43具有产蛋白酶、淀粉酶和纤维素酶3种消化酶的能力;粪肠球菌V20、蜡样芽孢杆菌V19和维德曼氏芽孢杆菌V22均具有产蛋白酶的能力。【结论】马蜂肠道细菌资源较丰富,部分有产消化酶的功能,可帮助马蜂消化食物,对宿主健康有一定影响。本研究筛选的6个菌株都能产蛋白酶,其中菌株V43和V44分别具有最强产淀粉酶和脂肪酶的能力,是可进一步开发利用的肠道功能菌株资源。     

云斑尖塘鳢消化酶活力的研究

本文采用酶学分析方法研究了云斑尖塘鳢在正常摄食状态与饥饿的状态下胃、肠及肝胰脏组织中蛋白酶、淀粉酶和脂肪酶的活性。结果显示,在30℃的条件下,正常摄食组样本在酸性条件下的蛋白酶活力表现为:胃后肠肝胰脏前肠,中性和碱性条件下:后肠肝胰脏前肠及胃;饥饿组样本仅有胃表现出较高的酸性蛋白酶活性,其他器官的蛋白酶活性均很低。在正常和饥饿实验组中肝胰脏的淀粉酶活性均高于其他器官,胃肠的淀粉酶活性均较低。正常摄食组中脂肪酶活力后肠肝胰脏;而在饥饿组中仅有肝胰脏检测到脂肪酶活性。结果表明,云斑尖塘鳢适度饥饿组较正常摄食组消化酶活性大幅降低;其高蛋白酶活力及中等脂肪酶活力与其肉食性相一致;此外云斑尖塘鳢也具备少量的淀粉消化能力。     

卤虫投喂下长吻(鱼危)仔稚鱼消化酶发育和口宽变化的研究

采用酶学和形态学测定方法, 研究在投喂卤虫条件下长吻(鱼危)仔鱼4种主要消化酶: 胃蛋白酶、胰蛋白酶、脂肪酶和淀粉酶的活性变化以及长吻(鱼危)仔鱼口宽、全长变化。实验共进行13d, 实验结果表明: (1)长吻(鱼危)仔鱼全长、口宽的发育与其日龄表现出明显的线性正相关(R_TL²=0.974, R_MW²=0.964)。口宽与全长比值(MW/TL)在仔鱼开口后急剧下降, 并自7日龄开始维持在0.07—0.08, 口宽和全长处于同步发育期并表现出明显的相关性(R²=0.948), 说明7日龄(/h, days post hatching)后口宽和全长处于同步发育期, 标志仔鱼转食的开始。(2)长吻(鱼危)仔鱼初次开口时即可检测出四种消化酶的活性。5—7/h时胰蛋白酶显著高于初孵仔鱼, 与此时仔鱼开始开口摄食的行为相一致。胃蛋白酶、脂肪酶活性在仔鱼孵化后第7天即开口的第3天, 淀粉酶活性在孵化后第6天, 显著高于初次孵化出来的仔鱼。8—13/h时, 胃蛋白酶、胰蛋白酶、脂肪酶和淀粉酶活性均在较高水平平稳的波动, 标志着消化道发育逐渐健全。     

The effect of adipokinetic hormones on the activity of digestive enzymes

The role of the adipokinetic hormone (AKH) in the control of protease, amylase and lipase activities is examined using the cockroach Periplaneta americana and the fruit fly Drosophila melanogaster as model species. The effects of Peram‐CAH‐I and ‐II on the activity of cockroach digestive enzymes in the gastric caeca and midgut are measured both in vivo and in vitro. The results show the activity of proteases, amylases and lipases in both parts of the gut: amylase activity is higher in the gastric caeca than in the midgut; lipase activity presents the opposite trend; and protease activity is similar in both organs. The applied hormones stimulate the activity of all digestive enzymes, although this stimulation is not uniform; AKHs affect enzymes selectively, and in some cases unequally, in the gastric caeca and midgut. No substantial differences between Peram‐CAH‐I and ‐II stimulation are recorded. The in vitro results demonstrate that AKH stimulates digestive enzyme activity directly. In agreement with the cockroach results, enzymatic activity in D. melanogaster larvae producing nonfunctional AKH is lower than that in the larvae with ectopically expressed Akh gene, where enzyme activity reaches or even exceeds that of the controls. Overall, the results demonstrate the active role of AKHs in the stimulation of digestive enzyme activity in insects.     

Immunohistochemical Identification of Met-Enkephalin in Digestive System and Its Effect on Digestive Enzyme Activities of the Scallop <Emphasis Type="Italic">Chlamys farreri</Emphasis>

The study was designed to determine whether methionine-enkephalin (M-ENK) was present in the digestive system of the scallop Chlamys farreri and investigate the effects of M-ENK on the activity of amylase, protease and lipase in the digestive system of C. farreri. The results indicated that M-ENK-like material was present in the epithelium and connective tissue of labial palps, mouth labia, stomach, intestine, rectum, and hepatopancreas of the scallop C. farreri. Moreover, it was also found that many isolated small cells showing M-ENK-like immunoreactivity were scattered in the epithelial layer of intestine, and many isolated big epithelial cells showing M-ENK-like immunoreactivity were scattered in tubules of hepatopancreas of the scallop. The activity levels of amylase and lipase in crystalline style, hepatopancreas and intestine were enhanced at 1 h after injection of exogenous M-ENK into adductor muscle of the scallops, whereas protease activity levels were significantly suppressed. Our report constitutes the first characterization of M-ENK in the digestive system of scallop C. farreri and investigates the effects of M-ENK on the activities of digestive enzymes of mollusk for the first time. The results suggest an involvement of M-ENK in the functional regulation of the digestive system of C. farreri.     

杜比亚蟑螂肠道菌的分离鉴定及产消化酶功能菌株的筛选

【背景】杜比亚蟑螂(Blaptica dubia)可用于活体饲料、化妆品和医药保健品的生产,其肠道菌的研究对杜比亚蟑螂的饲养和肠道菌资源的开发与利用都十分重要。【目的】揭示杜比亚蟑螂肠道可培养菌的种类,筛选具有产消化酶功能的菌株,为理解肠道菌对宿主的影响机理及功能菌株的利用提供科学依据和研究材料。【方法】采用体外培养法获得杜比亚蟑螂肠道菌,结合形态学和分子生物学方法进行鉴定;用水解圈法分别筛选产纤维素酶、蛋白酶、脂肪酶和淀粉酶菌株。【结果】在杜比亚蟑螂肠道中共分离出4属7种细菌,其中芽孢杆菌属(Bacillus)2种,沙雷氏菌属(Serratia)和柠檬酸杆菌属(Citrobacter)各2种,肠球菌属(Enterococcus)1种。从获得的20个菌株中筛选出10个具有产消化酶功能的菌株。其中,芽孢杆菌属的菌株D6、D12和D20具有产纤维素酶、蛋白酶、淀粉酶及脂肪酶4种消化酶的功能;沙雷氏菌属的菌株D3、D7、D9、D11和D15具有产纤维素酶、蛋白酶和脂肪酶3种消化酶的能力;柠檬酸杆菌属的菌株D5具有产纤维素酶的功能;肠球菌属的菌株D17具有产蛋白酶的能力。【结论】杜比亚蟑螂肠道多种细菌具有产消化酶帮助降解大分子营养物质的功能,可通过协助食物消化影响宿主健康。菌株D12、D7和D11分别具有最强产纤维素酶、蛋白酶和脂肪酶的能力,是可进一步开发利用的肠道功能菌株资源。     

Postprandial changes in pH and enzyme activity from the stomach and intestines of Tilapia rendalli (Boulenger, 1897), Oreochromis mossambicus (Peters, 1852) and Clarias gariepinus (Burchell, 1822)

The ability to utilise dietary components differs among fish species. Digestive enzymes may be used to determine the efficiency of the digestive process. In this study, the activities of the digestive enzymes in Tilapia rendalli, Oreochromis mossambicus and Clarias gariepinus were explored. Protease, amylase, lipase and cellulase activities were measured in different parts of the digestive tract of the three fish species. The pH dynamics along the digestive tract were monitored. In all fish species, the presence of food led to a reduction in stomach pH, whereby pH values of 1.54, 1.58 and 2.01 were recorded 12 h after feeding in O. mossambicus, T. rendalli and C. gariepinus, respectively. Protease and amylase activities were significantly higher (P < 0.05, anova ) in the tilapias than in C. gariepinus. The tilapias may be pre‐adapted to produce more protease and amylase to digest plant material, which is more difficult to digest than animal matter. In all species amylase activity was significantly higher in the proximal intestine than in the other parts of the digestive tract (P < 0.05, anova ). The highest protease activity was recorded in the distal intestines. This is because of the alkaline pH recorded in the proximal and distal intestines, which favours amylase and protease activity, respectively. Lipase activities were significantly higher (P > 0.05) in C. gariepinus than in both tilapias. Marginal cellulase activities were recorded in all species. It is inferred here that phylogeny and not diet may be the main factor influencing enzyme activities, as all fish were fed a similar diet.     

虎纹蛙消化道淀粉酶和脂肪酶活力研究

以酶学分析方法研究了虎纹蛙消化道淀粉酶和脂肪酶的分布以及pH和温度对这两种消化酶活力的影响。结果表明：在各自生理pH值条件下,虎纹蛙消化道不同部位淀粉酶活力大小顺序依次为前肠〉中肠〉后肠〉食道〉胃,胃和肠淀粉酶最适pH值分别为8．6和7．0,最适温度分别为35℃和40℃。脂肪酶活力大小顺序依次为中肠〉后肠〉前肠〉胃〉食道,各部位之间差异显著（P〈0．05）,胃和肠脂肪酶的最适pH值均为9．0,最适温度分别为50℃和55℃。     

Digestive enzyme activity of two stonefly species (Insecta, Plecoptera) and their feeding habits

The digestive enzymes of two stoneflies species, Hemimelaena flaviventris and Isoperla morenica, were studied for the first time. These species are temporary water inhabitants and exhibit great feeding plasticity. Although they are traditionally referred to as predators, a previous study revealed that H. flaviventris incorporates some diatoms into its diet in addition to feeding usually on several prey, and I. morenica (in that study under the name of I. curtata) only feeds on animals occasionally. The enzymatic activities of digestive amylase, lipase, protease, trypsin and chymotrypsin were determined for each species at the same developmental stage. The results show that H. flaviventris has a greater digestive enzymatic pool and higher relative and absolute protease, lipase and trypsin activities than I. morenica. The latter has a relative higher amylase activity. As higher amylase activity is typical of phytophagous species and higher protease activity typical of carnivorous species; these results reveal that H. flaviventris is a more efficient zoophagous species than I. morenica. The ecological implications of these findings, including the higher secondary production of H. flaviventris in its habitat, are discussed.     

Exocellular enzyme activity of dermatophytes and other fungi isolated from ruminants in Southern Iraq

Sixteen fungal species were isolated from 182 specimens collected from four ruminants (buffalo, camel, cattle and sheep) in Southern Iraq. Fungi represented by five species of dermatophytes and eleven species of other fungi were screened for the activity of four enzymes; keratinase, proteinase, lipase and amylase. Keratinase was found to be produced by all of the dermatophytes and non-dermatophytes, except for Paecillomyces variottii and Scytalidium lignicola. However, high keratinase activity was expressed by the dermatophytic species particularly by Trichophyton mentagrophytes var. erinacei and Microsporum gypseum. Three dermatophytes viz. M. gypseum, T. verrucosum and T. mentagrophytes var. nodulare were capable of producing protease, lipase and amylase. Although, T. mentagrophytes var. erinacei showed high protease activity, it did not produce lipase and amylase. On the contrary most of the non-dermatophytic species revealed protease and lipase activities higher than the dermatophytes. The Curvularia spp. isolates showed the highest protease and amylase activity, while Aspergillus parasiticus revealed the highest activity of lipase and amylase. No correlation was observed between enzyme activity and the growth rate of the examined fungi. This revised version was published online in June 2006 with corrections to the Cover Date.     

福寿螺和田螺消化酶活性比较

为比较福寿螺(Pomacea canaliculata(Lamarck,1828))和当地中国圆田螺(Cipangopaludina chinensis(Gray,1832))消化能力的差异,探索福寿螺成功入侵的机制,以田螺为对照,测定了1—4龄的福寿螺和田螺的胃和肝脏的消化酶——纤维素酶(羧甲基纤维素法)、淀粉酶(3,5-二硝基水杨酸法)和脂肪酶(滴定法)的活性。结果表明:1)相同年龄的福寿螺胃和肝脏中的消化酶活性明显高于田螺。其中,纤维素酶活性分别高出1.00—2.11倍、1.66—2.84倍;淀粉酶活性分别高出1.53—3.47倍、1.47—1.80倍;脂肪酶活性分别高出2.07—4.73倍、6.13—9.93倍。2)在生长发育过程中,福寿螺胃和肝脏中的消化酶活性变化幅度(51.2%—131.2%)明显高于田螺(23.3%—47.1%)。3)福寿螺的各种消化酶之间存在协同作用。如福寿螺的淀粉酶活性与脂肪酶活性呈极显著正相关(胃中r=0.736**、肝脏中r=0.867**)。此外,胃中的淀粉酶活性还与纤维素酶活性呈显著正相关关系(r=0.696*)。相应地,田螺胃中的淀粉酶和脂肪酶之间也存在显著的正相关关系(r=0.706*),而肝脏中的纤维素酶与脂肪酶活性呈显著负相关(r=-0.593*)。4)福寿螺对纤维素类和淀粉类物质都有较强的消化能力,且能较好地消化脂肪类物质,而田螺能消化纤维素类和淀粉类物质,对脂肪的消化能力却很弱。福寿螺的纤维素酶和淀粉酶活性分别是田螺的2.42和1.88倍,脂肪酶活性达到了5.66倍。可见,福寿螺具有较高的消化酶活性,且各消化酶之间存在正协同性。这可能是导致福寿螺食量大、食性杂,使其能快速生长和成功入侵的重要原因之一。     

不同生态环境中铜绿丽金龟幼虫肠道细菌 产消化酶活性比较

目的测定不同生态环境中铜绿丽金龟幼虫肠道细菌产消化酶活性。方法采用平板透明圈法和分光光度计法。结果平板透明圈法测得废弃菜园和花生田中铜绿丽金龟幼虫肠道细菌产蛋白酶和淀粉酶活性差异无统计学意义(F=1.089、0.4963,P0.05),而细菌的产纤维素酶活性有显著差异,其中花生田铜绿丽金龟幼虫肠道中分离到的粘质沙雷菌产酶活性显著高于其他菌株;分光光度计测得的不同生态环境中铜绿丽金龟幼虫肠道细菌的产蛋白酶、淀粉酶和纤维素酶活性差异均有统计学意义(F=461.565、42.349、18.7673,P0.05)。从变异系数来看,分光光度计法测得的蛋白酶、淀粉酶和纤维素酶的变异程度较低,而脂肪酶测定时平板透明圈法的变异系数较低。结论平板透明圈法和分光光度计法均可用于铜绿丽金龟幼虫肠道细菌产消化酶活性测定。通过分析研究比较,分光光度计法适于测定细菌的产蛋白酶、淀粉酶和纤维素酶活性,平板透明圈法适于测定细菌的产脂肪酶活性。     

Polymorphism and partial characterization of digestive enzymes in the spiny lobster Panulirus argus

We characterized major digestive enzymes in Panulirus argus using a combination of biochemical assays and substrate-(SDS or native)-PAGE. Protease and amylase activities were found in the gastric juice while esterase and lipase activities were higher in the digestive gland. Trypsin-like activity was higher than chymotrypsin-like activity in the gastric juice and digestive gland. Stability and optimal conditions for digestive enzyme activities were examined under different pHs, temperature and ionic strength. The use of protease inhibitors showed the prevalence of serine proteases and metalloproteases. Results for serine proteases were corroborated by zymograms where several isotrypsins-like (17-21 kDa) and isochymotrypsin-like enzymes (23-38 kDa) were identified. Amylases (38-47 kDa) were detected in zymograms and a complex array of non-specific esterases isoenzymes was found in the digestive gland. Isoenzyme polymorphism was found for trypsin, amylase, and esterase. This study is the first to evidence the biochemical bases of the plasticity in feeding habits of P. argus. Distribution and properties of enzymes provided some indication on how the digestion takes place and constitute baseline data for further studies on the digestion physiology of spiny lobsters.     

Diversity of Yeasts from Puddles in the Vicinity of Midre Lovénbreen Glacier, Arctic and Bioprospecting for Enzymes and Fatty Acids

A total of 132 yeast strains were characterised from 4 sediment samples collected from small puddles in the vicinity of Midre Lovénbreen glacier, Arctic. Based on the D1/D2 domain sequence similarity, the isolates could be categorised into 6 groups. The nearest phylogenetic neighbour of groups I to VI were identified as Cryptococcus gastricus, Cryptococcus terricolus, Rhodotorula muscorum, Mrakia psychrophila, Mrakia gelida and Rhodotorula glacialis, respectively. Strains representative of the six groups were psychrophilic and salt tolerant but varied in their ability to produce cold-active extracellular enzymes such as lipase, protease, pectinase, cellulase and amylase. C_{18:1 (w9C)} and C_{18:2 (w9,12C)} were the only two fatty acids common to all the yeasts and branched and (or) unsaturated fatty acids increased in yeasts growing at 8°C compared to 22°C, probably as an adaptation to low temperature. The present study establishes that psychrophilic yeasts are predominant in Arctic and could be used as work horses to produce cold-active enzymes and poly unsaturated fatty acids which have been implicated in low temperature adaptation and also for their use in biotechnology.     

The effects of copper, iron and zinc on digestive enzyme activity in the hybrid tilapia Oreochromis niloticus (L.) ×Oreochromis aureus (Steindachner)

The present experiment was conducted to study effects of Cu, Fe and Zn on activities of digestive enzymes of the hybrid tilapia Oreochromis niloticus×Oreochromis aureus. The acidic protease activities increased 65·5 and 55·1% by addition of homogenates of digesta‐containing stomach with copper (75 mg l⁻¹) and zinc (50 mg l⁻¹) respectively. Addition of Cu and Zn increased the activities of protease in the hepatopancreas homogenates by 132·7 and 38·1% respectively, and reduced the activity of protease in the digesta‐containing intestine homogenates by 11·0 and 13·8% respectively. Addition of Fe (50 mg l⁻¹) increased the acidic protease activity by 96·7% but did not alter the activities of protease in the intestine and hepatopancreas. Addition of Cu markedly inhibited activities of amylase in intestine and hepatopancreas homogenates, while Zn addition showed no effects. Addition of Fe reduced activities of amylase in the intestine homogenates by 47·9% but had no effect on amylase activities in the hepatopancreas. When Cu (75 mg kg⁻¹), Fe (50 mg kg⁻¹) and Zn (50 mg kg⁻¹) were supplemented to basal diet for 3 weeks, the activities of amylase in hepatopancreas homogenates increased 125·3, 215·6 and 70·0%, respectively, the activities of amylase in intestine increased 79·8, 74·6 and 48·5%, respectively, and the activities of lipase in intestine increased 90·5, 149·8 and 84·0%, respectively. Supplementation of Cu, Fe or Zn into diet had no effects on activity of protease in all digestive organs. Therefore, the results suggest that effects of Cu, Fe and Zn on activity of digestive enzymes in vitro were different from those seen in vivo, and that the positive effects of Cu, Fe and Zn supplemented to fish diet would be valuable information for formulating fish feed.     

Digestive enzymes of two brachyuran and two anomuran land crabs from Christmas Island,Indian Ocean

The digestive ability of four sympatric land crabs species (the gecarcinids, Gecarcoidea natalis and Discoplax celeste and the anomurans, Birgus latro and Coenobita perlatus) was examined by determining the activity of their digestive enzymes. The gecarcinids are detritivores that consume mainly leaf litter; the robber crab, B. latro, is an omnivore that preferentially consumes items high in lipid, carbohydrate and/or protein; C. perlatus is also an omnivore/detritivore. All species possess protease, lipase and amylase activity for hydrolysing ubiquitous protein, lipid and storage polysaccharides (glycogen and starch). Similarly all species possess enzymes such as N-acetyl-β-d-glucosaminidase, the cellulases, endo-β-1,4-glucanase and β-glucohydrolase and hemicellulases, lichenase and laminarinase for the respective hydrolysis of structural substrates chitin, cellulose and hemicelluloses, lichenan and laminarin. Except for the enzyme activities of C. perlatus, enzyme activity could not be correlated to dietary preference. Perhaps others factors such as olfactory and locomotor ability and metabolic status may determine the observed dietary preferences. The digestive fluid of C. perlatus possessed higher endo-β-1,4-glucanase, lichenase and laminarinase activities compared to that of the other species. Thus, C. perlatus may be efficient at digestion of cellulose and hemicellulose within plant material. Zymography indicated that the majority of protease, lipase, phosphatase, amylase, endo-β-1,4-glucanase, β-glucohydrolase and N-acetyl-β-d-glucosaminidase isozymes were common to all species, and hence were inherited from a common aquatic ancestor. Differences were observed for the phosphatase, lipase and endo-β-1,4-glucanase isozymes. These differences are discussed in relation to phylogeny and possible evolution to cope with the adoption of a terrestrial diet.     

Digestive protease,lipase and amylase activities in stage i larvae of the american lobster,Homarus americanus

• 1.1. Digestive protease, lipase, and amylase of Stage I larvae of the American lobster Homarus americanus are characterized.
• 2.2. A sensitive method for detection of crustacean lipase was developed using an latroscan which combines thin-layer chromatography and flame ionization detection to quantify free fatty acids generated by lipase digestion.
• 3.3. pH optima of the three enzymes occurred at or near the pH of gastric fluid.
• 4.4. A time course study demonstrated slight increases in protease and amylase activities during the first larval stage, regardless of whether the lobsters were fed or not, whereas lipase activity was constant.

     

Effect of formulated diet on digestive enzymes of Labeo rohita (Ham.)

Six sets of feeding experiments were carried out using formulated diets containing prawn head waste (PW), chicken intestine waste (CW), banana flower (BF), cauliflower waste (CAU) Dolicos lab lab (DLL) and groundnut leaf (GNL) in four levels of inclusion (15, 30, 45 and 60%) to assess the pattern of distribution and activities of digestive enzymes like cellulase, amylase, maltase, invertase, protease and lipase in the digestive tracts of Labeo rohita fingerlings. A control group of fish was fed with diets containing antibiotics to destroy the digestive tract microflora which may induce digestive functions. In general, the activity of digestive enzymes depended on the amount and type of the ingredients present in the diets ingested by the fish. Test animals showed both endogenous and bacterial cellulase activities which suggests the necessity for including cellulose (plant protein source) as dietary ingredient. Occurrence of higher amount of cellulase in the foregut and amylase in the fore and midgut influenced by DNL and GNL diets revealed the possibility of including less than 40% of the respective ingredients in the diet of rohu. Maltase and invertase were highly influenced by GNL, DLL and BF diets than PW and CW diets. More than 40% inclusion of PW and CW was found to increase protease and lipase secretion in the midgut and hindgut regions. The higher secretion of lipase in the midgut suggested the physiological versatility for lipid digestion in rohu fingerlings.