近日，澳大利亚CSIRO高级研究员Nick博士和上海海洋大学吴旭干教授收到“International Aquafeed”杂志社的邀请，就“雨生红球藻虾青素在鲑鳟鱼上的应用研究进展”向水产饲料界做一个概述性介绍。

今天，我们带着大家一起去看一看。

Algal carotenoids as pigments for salmonids.

藻类类胡萝卜素作为鲑鱼的色素。

Dr Nick Wade - Senior Research Scientist, CSIRO Agriculture and Food, Australia; and Dr Xugan Wu – Director of Department of Aquaculture Nutrition and Feed, Shanghai Ocean University, China （Nick Wade博士——澳大利亚CSIRO农业和食品高级研究科学家；中国上海海洋大学水产营养与饲料系主任吴旭干博士）

Carotenoids provide the intense red colouration of salmonid muscle through the dietary inclusion of the synthetic pigment astaxanthin (Axn). In aquaculture, synthetically derived Axn is the predominant source included in aquafeeds due to the lower cost of production. Alternative sources of carotenoids from bacteria, yeast or algae have been under development for decades but have not been widely adopted, largely due to increased cost. As natural antioxidants, carotenoids neutralise free radicals and in humans have been shown to prevent or slow down chronic diseases, cellular damage and aging. Specifically, they are known to reduce the risk of inflammation, heart disease, and cancer, type 2 diabetes, chronic eye and macular diseases, obesity, and neurodegenerative disorders (Sathasivam et al 2018).

中译：通过在饮食中添加合成色素虾青素(Axn)，类胡萝卜素可使鲑鱼肌呈现强烈的红色。在水产养殖中，由于生产成本较低，合成虾青素是添加的主要来源。几十年来，人们一直在开发从细菌、酵母或藻类中提取类胡萝卜素的替代来源，但一直没有被广泛采用，这主要是由于成本较高。作为天然的抗氧化剂，类胡萝卜素可中和自由基，预防或减缓人体慢性病，细胞损伤和衰老。具体来说，可以降低炎症、心脏病、癌症、2型糖尿病、慢性眼睛和黄斑疾病、肥胖和神经退行性疾病的风险(Sathasivam等人，2018年)。

Scalable and cost effective production of algal carotenoids

海藻类胡萝卜素的规模化生产和成本效益

Considerable progress has been made in the production of carotenoids from algae, encompassing multiple algal species and carotenoid compounds (Ambati et al 2019). The freshwater microalga Hematoccocus pluvialis shows great potential as a source of natural pure Axn. It can be grown from pure flask cultures to vast expanses of enclosed photobioreactors (Figure 1) for use in the nutraceutical, cosmetic, and food industries. Through years of culture innovation, Yunnan Alphy has been able to produce up to 160 tonnes of algal biomass annually at an Axn content of 3-5%.

After optimising and expanding algal biomass during the green growth phase, stressful conditions such as strong sunlight, water chemistry and temperature, cause the algae to produce Axn as a way for the cell to protect itself against the “tough” environment. This causes the algae to change from green to red. The Axn accumulation period is around 15 to 22 days depending on the season with production conducted throughout the year. The product holds many production and safe food certifications such as organic and EU novel foods. Such scale of production and Axn content now makes algal carotenoids a realistic alternative for aquaculture.

中译：藻类类胡萝卜素量产已经取得了相当大的进展，包括多种藻类物种和类胡萝卜素化合物(Ambati等，2019年)。淡水微藻雨生红球藻是天然纯虾青素的优质提取物。它可以从纯烧瓶培养，到光密闭生物反应器累积(图1)，主要用于营养，化妆品和食品工业。通过多年的培养创新，云南爱尔发每年能够生产高达160吨的藻粉，虾青素含量为3-5%。

在绿色生长阶段优化和扩大藻类生物量后，强烈的阳光、水化学和温度等压力条件导致藻类产生虾青素，这是细胞以此保护自己免受“艰苦”环境的一种方式。这导致藻类从绿色变成红色。根据季节的不同，虾青素积累时间约为15 - 22天，全年不间断生产。该产品拥有许多生产和安全食品认证，如有机认证和欧盟新资源食品。这样的生产规模和虾青素含量使得藻类类胡萝卜素应用于水产养殖成为可能选择。

Figure 1 – H. pluvialis production facility in southern China (Photo: Yunnan Alphy Biotech Pty Ltd) 中国南部雨生红球藻生产基地（图片来源:云南爱尔发生物科技有限公司）

Comparison of pigment sources in trout

鳟鱼色素来源的比较

In a recent trial (Wang et al, unpublished) under commercial conditions, rainbow trout were grown from 0.6 kg to over 2 kg on diets that contained 30 mg/kg Axn from different sources: Synthetic Axn (Carophyll Pink); Yeast Axn – Phaffia rhodozyma; Algal Axn – H. pluvialis; No Axn – no additional supplementation. Results showed that Axn source did not affect weight gain, somatic indices or flesh pigmentation, demonstrating that each carotenoid source had no effect on production performance or product quality.

However, the liver of fish fed algal carotenoids had significantly increased total antioxidant capacity, while total lipid content was significantly increased in the muscle. These results suggest that there could be additional benefit of algal Axn during periods of increased environmental stress. All carotenoid sources represent viable commercial options for producing healthy fish with high quality fillet attributes.

中译：在最近的一项商业条件下试验中(Wang 等，未发表)，虹鳟鱼从0.6公斤长到超过2公斤，饲料中含有30毫克/公斤来自不同来源的虾青素：人工合成虾青素；红法夫酵母虾青素；雨生红球藻虾青素；未添加虾青素的对照组。结果表明，不同虾青素不会影响增重、躯体指数和色素沉积，因此不会影响养殖性能和品质。

但是，饲喂红球藻虾青素组鱼体肝脏的总抗氧化能力显著提高，肌肉中的总脂含量显著增加。这些结果表明，在养殖环境压力存在时（如：高温等），红球藻虾青素能够提高鱼类的养殖效果，如：提高摄食量和抗氧化能力。鱼类养殖企业可以根据自身需求，选择合适的类胡萝卜素来源进行品质调控。

Figure 2 – Pigmentation of trout muscle with different Axn sources (Photo: Lei Wang, Shanghai Ocean University) 图2 -不同虾青素来源的鳟鱼肌肉色素沉着(图片来源：上海海洋大学王磊)

Improved digestibility of algal carotenoids in Atlantic salmon

提高大西洋鲑鱼藻类类胡萝卜素的消化率

Typically included at 50-60 ppm, dietary Axn can account for up to 25% of the cost of diet. However, overall retention in the muscle often less than 10%. The digestion, absorption and deposition of Axn is affected by factors including Axn source, dietary inclusion level and the ingredient composition of the diets. Axn from algae is esterified, a natural modification where a fatty acid is attached to one or both ends of the carotenoid molecule, which can also impact digestion. In a study on Atlantic salmon (Courtot et al 2022), apparent digestibility (AD) of algal Axn was shown to be significantly higher than synthetic Axn.

Furthermore, the AD of Axn was shown to be enhanced by the dietary inclusion of canola oil rather than poultry oil or tallow (Figure 3). These oils differ markedly in their fatty acid composition, with canola oil enriched with mono-unsaturated fatty acids (MUFA), while tallow was enriched with saturated fatty acids (SFA). This led to the finding that Axn digestibility was significantly positively correlated with dietary MUFA content, especially 18:1n-9cis as one of the main fatty acids in canola oil. This result provides evidence that the type and composition of oil provides significant improvement of algal Axn digestibility, which is expected to lead to improved utilisation and muscle retention.

In summary, the inclusion of algal biomass as a source of natural Axn combined with the inclusion of MUFA rich oils such as canola can lead to significant improvements in the utilisation of dietary Axn, and therefore the more cost-effective production of high-quality Atlantic salmon.

中译：三文鱼饲料中通常添加50- 60ppm的虾青素，虾青素最高可占饲料成本的25%。但是，三文鱼肌肉对饲料中的虾青素保留率通常低于10%。虾青素的消化、吸收和沉积受多种因素影响，包括虾青素来源，添加水平和饲料组分。红球藻虾青素是酯化的，脂肪酸结合在游离类胡萝卜素分子的一端或两端，这种变化也会影响水产动物对虾青素的消化和吸收。课题组最近对大西洋鲑鱼的研究表明：三文鱼对红球藻虾青素的表观消化率(AD)明显高于合成虾青素(Courtot et al 2022)。

此外，饲料中添加菜籽油比禽油或牛油更会增强虾青素的表观消化率(图3)。这些油脂的脂肪酸组成存在显著差异，菜籽油富含单不饱和脂肪酸(MUFA)，而牛油富含饱和脂肪酸(SFA)。由此可见，虾青素消化率与饲料中MUFA的含量呈显著正相关，特别是18 - 1n-9的含量。这个研究结果证明油脂种类及脂肪酸组成会显著影响鱼类对红球藻虾青素的消化率。

综上所述，添加红球藻来源的天然虾青素，结合添加富含MUFA的菜籽油，可以显著提高饲料中虾青素的利用率，从而降低饲料成本，生产出更高性价比的高质量大西洋鲑鱼。

Figure 3 Apparent digestibility (AD% digested) of carotenoids for the four experimental diets and positive correlation of carotenoid AD with dietary mono-unsaturated fatty acid (MUFA) levels (adapted from Courtot et al 2022).图3 四种试验饲粮中类胡萝卜素的表观消化率(AD%消化率)以及类胡萝卜素表观消化率与饲粮中单不饱和脂肪酸(MUFA)水平的正相关关系(适配自Courtot等人，2022年)。

References

Ambati, R. R., D. Gogisetty, R. G. Aswathanarayana, S. Ravi, P. N. Bikkina, B. Lei and Y. P. Su (2019). Industrial potential of carotenoid pigments from microalgae: Current trends and future prospects. Critical Reviews in Food Science and Nutrition 59(12): 1880-1902.

Courtot, E., D. Musson, C. Stratford, D. Blyth, N. A. Bourne, A. N. Rombenso, C. J. Simon, X. G. Wu and N. M. Wade (2022). Dietary fatty acid composition affects the apparent digestibility of algal carotenoids in diets for Atlantic salmon, Salmo salar. Aquaculture Research 53(6): 2343-2353.

Sathasivam, R., & Ki, J. S. (2018). A review of the biological activities of microalgal carotenoids and their potential use in healthcare and cosmetic industries. Marine drugs, 16(1), 26.

Wang L, Long X, Sun W, Li Y, Wang X, Zhang Y and Wu X (2022). Effects of three different sources of dietary Axn on the growth performance, coloration, and antioxidant capacity of rainbow trout Oncorhynchus mykiss. under review

作者：Nick博士&吴旭干教授，特别鸣谢