湛江沿海礁膜属海藻分类学鉴定和典型样品的营养成分

Taxonomic identification of Monostroma from the Zhanjiang coastal area and nutritional ingredient analysis of typical sample

摘要:

目的 确定湛江沿海礁膜属海藻的种类及其典型采样点样品营养学成分。方法 首先运用形态学与分子学相结合的方法对采集于湛江沿海的礁膜属海藻进行分类学鉴定，然后参照国标法对典型采样点样品的主要营养成分、氨基酸组成及矿物质含量进行测定，并进行营养学评价。结果 湛江沿海礁膜属海藻具有相似的形态学特征；藻体颜色呈绿色、浅绿色，单层膜状；藻体平均长度为9.19~11.12 cm、宽度为6.85~8.16 cm、厚度为35.20~38.80 μm，藻体表面细胞为圆角多边形，平均长度为11.14~11.42 μm，宽度为7.25~8.48 μm，主要含有1个蛋白核 (≥88%)。湛江沿海礁膜属海藻样品的ITS序列与来自广西防城港礁膜 (AF415170)的处于同一分支，且贝叶斯后验概率、最大似然法自展值和邻接法自展值分别高达0.99、88%和99%。此外，湛江礁膜属海藻的水分 (16.26%)含量较高，灰分 (16.17%)、粗蛋白 (10.50%)和粗脂肪 (1.37%)含量适中；脂肪酸种类多，包括饱和脂肪酸 (78.57%)与不饱和脂肪酸 (21.43%)； 氨基酸种类齐全，必需氨基酸 (39.02%)与呈味氨基酸 (47.93%)含量丰富，符合FAO/WHO标准模式的要求。结论 湛江沿海礁膜属海藻种类单一，均为礁膜，且湛江沿海礁膜营养成分丰富、营养价值高，具有广阔的食用和药用前景。本研究可为湛江沿岸礁膜属海藻的进一步探究及资源化利用提供基础数据支撑。

Abstract:

Monostromatic green algae, characterized by fronds composed solely of horizontally arranged single cell layers, are widely distributed in temperate to tropical seas worldwide. Monostroma (Thuret 1854), Gayralia (Vinogradova 1969), and Protomonostroma (Vinogradova 1969) are among the primary genera of monostromatic green algal. Monostroma (Chlorophyta, Ulvophyceae) is cosmopolitan and includes 55 species, of which only 32 are currently taxonomically confirmed. Several species of Monostroma are attracting global attention due to their economic importance, particularly in the food and cosmetic industries. Additionally, chemicals with antiviral and anticoagulant properties have recently been isolated from some species of the Monostroma genus. Zhanjiang city, surrounded by the sea on three sides and possessing a long coastline (2 325.9 km), is rich in wild Monostroma species. To determine the identity of Monostroma species from the Zhanjiang coastal area and analyze their nutritional composition, this study examined the morphological characteristics (thallus type, size, color; cell size, shape, and arrangement; chloroplast shape, position, and pyrenoid number) and nuclear-encoded Internal Transcribed Spacer (ITS) phylogenetics of collected Monostroma species. Subsequently, the main nutrient composition (crude protein, ash, moisture, and crude fat), amino acid content, and mineral composition were determined using national standard methods to evaluate their nutritional value. Morphological observations revealed that Monostroma thalli with similar morphology exhibited green or light green colors, had a single-cell layer, and measured approximately 9.19-11.12 cm in length, 6.85-8.16 cm in width, and 35.20-38.80 μm thickness. Surface cells were irregular, polygonal, or rounded polygons, with dimensions of 11.14-11.42 μm in length and 7.25-8.48 μm in width. These cells predominantly contained one pyrenoid (≥88%), occasionally two (≤8%), or three (≤4%). ITS sequence analysis showed that the Monostroma species had an identical nrITS sequence to M. nitidum (AF415170) from Fangchenggang of Guangxi, China, with support values of 0.99 for Bayesian posterior probabilities, 88% for ML bootstrap, and 99% for NJ distance bootstrap. Therefore, all the Monostroma species in Zhanjiang coastal area should be identified as Monostroma nitidum. Nutrient composition analysis revealed that M. nitidum had high water content (16.26%), moderate ash (16.17%), crude protein (10.50%), and crude fat (1.37%) contents. M. nitidum contained a variety of fatty acids, including saturated fatty acids (78.57%) and unsaturated fatty acids (21.43%). The amino acid profile was diverse, with essential amino acids (39.02%) and flavor amino acids (47.93%) meeting the FAO/WHO standard model. Thus, M. nitidum along the Zhanjiang coastal area held significant economic value in the food and pharmaceutical industries due to its rich nutrients and high nutritional value. These findings enhanced our understanding of the nutrient value of M. nitidum and were expected to promote the healthy and rapid growth of the M. nitidum industry.